Merge branch 'rs/blame-code-cleanup'

[thirdparty/git.git] / builtin / blame.c

/*
 * Blame
 *
 * Copyright (c) 2006, 2014 by its authors
 * See COPYING for licensing conditions
 */

#include "cache.h"
#include "refs.h"
#include "builtin.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree-walk.h"
#include "diff.h"
#include "diffcore.h"
#include "revision.h"
#include "quote.h"
#include "xdiff-interface.h"
#include "cache-tree.h"
#include "string-list.h"
#include "mailmap.h"
#include "mergesort.h"
#include "parse-options.h"
#include "prio-queue.h"
#include "utf8.h"
#include "userdiff.h"
#include "line-range.h"
#include "line-log.h"
#include "dir.h"
#include "progress.h"

static char blame_usage[] = N_("git blame [<options>] [<rev-opts>] [<rev>] [--] <file>");

static const char *blame_opt_usage[] = {
        blame_usage,
        "",
        N_("<rev-opts> are documented in git-rev-list(1)"),
        NULL
};

static int longest_file;
static int longest_author;
static int max_orig_digits;
static int max_digits;
static int max_score_digits;
static int show_root;
static int reverse;
static int blank_boundary;
static int incremental;
static int xdl_opts;
static int abbrev = -1;
static int no_whole_file_rename;
static int show_progress;

static struct date_mode blame_date_mode = { DATE_ISO8601 };
static size_t blame_date_width;

static struct string_list mailmap = STRING_LIST_INIT_NODUP;

#ifndef DEBUG
#define DEBUG 0
#endif

/* stats */
static int num_read_blob;
static int num_get_patch;
static int num_commits;

#define PICKAXE_BLAME_MOVE              01
#define PICKAXE_BLAME_COPY              02
#define PICKAXE_BLAME_COPY_HARDER       04
#define PICKAXE_BLAME_COPY_HARDEST      010

/*
 * blame for a blame_entry with score lower than these thresholds
 * is not passed to the parent using move/copy logic.
 */
static unsigned blame_move_score;
static unsigned blame_copy_score;
#define BLAME_DEFAULT_MOVE_SCORE        20
#define BLAME_DEFAULT_COPY_SCORE        40

/* Remember to update object flag allocation in object.h */
#define METAINFO_SHOWN          (1u<<12)
#define MORE_THAN_ONE_PATH      (1u<<13)

/*
 * One blob in a commit that is being suspected
 */
struct origin {
        int refcnt;
        /* Record preceding blame record for this blob */
        struct origin *previous;
        /* origins are put in a list linked via `next' hanging off the
         * corresponding commit's util field in order to make finding
         * them fast.  The presence in this chain does not count
         * towards the origin's reference count.  It is tempting to
         * let it count as long as the commit is pending examination,
         * but even under circumstances where the commit will be
         * present multiple times in the priority queue of unexamined
         * commits, processing the first instance will not leave any
         * work requiring the origin data for the second instance.  An
         * interspersed commit changing that would have to be
         * preexisting with a different ancestry and with the same
         * commit date in order to wedge itself between two instances
         * of the same commit in the priority queue _and_ produce
         * blame entries relevant for it.  While we don't want to let
         * us get tripped up by this case, it certainly does not seem
         * worth optimizing for.
         */
        struct origin *next;
        struct commit *commit;
        /* `suspects' contains blame entries that may be attributed to
         * this origin's commit or to parent commits.  When a commit
         * is being processed, all suspects will be moved, either by
         * assigning them to an origin in a different commit, or by
         * shipping them to the scoreboard's ent list because they
         * cannot be attributed to a different commit.
         */
        struct blame_entry *suspects;
        mmfile_t file;
        struct object_id blob_oid;
        unsigned mode;
        /* guilty gets set when shipping any suspects to the final
         * blame list instead of other commits
         */
        char guilty;
        char path[FLEX_ARRAY];
};

struct progress_info {
        struct progress *progress;
        int blamed_lines;
};

static int diff_hunks(mmfile_t *file_a, mmfile_t *file_b,
                      xdl_emit_hunk_consume_func_t hunk_func, void *cb_data)
{
        xpparam_t xpp = {0};
        xdemitconf_t xecfg = {0};
        xdemitcb_t ecb = {NULL};

        xpp.flags = xdl_opts;
        xecfg.hunk_func = hunk_func;
        ecb.priv = cb_data;
        return xdi_diff(file_a, file_b, &xpp, &xecfg, &ecb);
}

/*
 * Prepare diff_filespec and convert it using diff textconv API
 * if the textconv driver exists.
 * Return 1 if the conversion succeeds, 0 otherwise.
 */
int textconv_object(const char *path,
                    unsigned mode,
                    const struct object_id *oid,
                    int oid_valid,
                    char **buf,
                    unsigned long *buf_size)
{
        struct diff_filespec *df;
        struct userdiff_driver *textconv;

        df = alloc_filespec(path);
        fill_filespec(df, oid->hash, oid_valid, mode);
        textconv = get_textconv(df);
        if (!textconv) {
                free_filespec(df);
                return 0;
        }

        *buf_size = fill_textconv(textconv, df, buf);
        free_filespec(df);
        return 1;
}

/*
 * Given an origin, prepare mmfile_t structure to be used by the
 * diff machinery
 */
static void fill_origin_blob(struct diff_options *opt,
                             struct origin *o, mmfile_t *file)
{
        if (!o->file.ptr) {
                enum object_type type;
                unsigned long file_size;

                num_read_blob++;
                if (DIFF_OPT_TST(opt, ALLOW_TEXTCONV) &&
                    textconv_object(o->path, o->mode, &o->blob_oid, 1, &file->ptr, &file_size))
                        ;
                else
                        file->ptr = read_sha1_file(o->blob_oid.hash, &type,
                                                   &file_size);
                file->size = file_size;

                if (!file->ptr)
                        die("Cannot read blob %s for path %s",
                            oid_to_hex(&o->blob_oid),
                            o->path);
                o->file = *file;
        }
        else
                *file = o->file;
}

/*
 * Origin is refcounted and usually we keep the blob contents to be
 * reused.
 */
static inline struct origin *origin_incref(struct origin *o)
{
        if (o)
                o->refcnt++;
        return o;
}

static void origin_decref(struct origin *o)
{
        if (o && --o->refcnt <= 0) {
                struct origin *p, *l = NULL;
                if (o->previous)
                        origin_decref(o->previous);
                free(o->file.ptr);
                /* Should be present exactly once in commit chain */
                for (p = o->commit->util; p; l = p, p = p->next) {
                        if (p == o) {
                                if (l)
                                        l->next = p->next;
                                else
                                        o->commit->util = p->next;
                                free(o);
                                return;
                        }
                }
                die("internal error in blame::origin_decref");
        }
}

static void drop_origin_blob(struct origin *o)
{
        if (o->file.ptr) {
                free(o->file.ptr);
                o->file.ptr = NULL;
        }
}

/*
 * Each group of lines is described by a blame_entry; it can be split
 * as we pass blame to the parents.  They are arranged in linked lists
 * kept as `suspects' of some unprocessed origin, or entered (when the
 * blame origin has been finalized) into the scoreboard structure.
 * While the scoreboard structure is only sorted at the end of
 * processing (according to final image line number), the lists
 * attached to an origin are sorted by the target line number.
 */
struct blame_entry {
        struct blame_entry *next;

        /* the first line of this group in the final image;
         * internally all line numbers are 0 based.
         */
        int lno;

        /* how many lines this group has */
        int num_lines;

        /* the commit that introduced this group into the final image */
        struct origin *suspect;

        /* the line number of the first line of this group in the
         * suspect's file; internally all line numbers are 0 based.
         */
        int s_lno;

        /* how significant this entry is -- cached to avoid
         * scanning the lines over and over.
         */
        unsigned score;
};

/*
 * Any merge of blames happens on lists of blames that arrived via
 * different parents in a single suspect.  In this case, we want to
 * sort according to the suspect line numbers as opposed to the final
 * image line numbers.  The function body is somewhat longish because
 * it avoids unnecessary writes.
 */

static struct blame_entry *blame_merge(struct blame_entry *list1,
                                       struct blame_entry *list2)
{
        struct blame_entry *p1 = list1, *p2 = list2,
                **tail = &list1;

        if (!p1)
                return p2;
        if (!p2)
                return p1;

        if (p1->s_lno <= p2->s_lno) {
                do {
                        tail = &p1->next;
                        if ((p1 = *tail) == NULL) {
                                *tail = p2;
                                return list1;
                        }
                } while (p1->s_lno <= p2->s_lno);
        }
        for (;;) {
                *tail = p2;
                do {
                        tail = &p2->next;
                        if ((p2 = *tail) == NULL)  {
                                *tail = p1;
                                return list1;
                        }
                } while (p1->s_lno > p2->s_lno);
                *tail = p1;
                do {
                        tail = &p1->next;
                        if ((p1 = *tail) == NULL) {
                                *tail = p2;
                                return list1;
                        }
                } while (p1->s_lno <= p2->s_lno);
        }
}

static void *get_next_blame(const void *p)
{
        return ((struct blame_entry *)p)->next;
}

static void set_next_blame(void *p1, void *p2)
{
        ((struct blame_entry *)p1)->next = p2;
}

/*
 * Final image line numbers are all different, so we don't need a
 * three-way comparison here.
 */

static int compare_blame_final(const void *p1, const void *p2)
{
        return ((struct blame_entry *)p1)->lno > ((struct blame_entry *)p2)->lno
                ? 1 : -1;
}

static int compare_blame_suspect(const void *p1, const void *p2)
{
        const struct blame_entry *s1 = p1, *s2 = p2;
        /*
         * to allow for collating suspects, we sort according to the
         * respective pointer value as the primary sorting criterion.
         * The actual relation is pretty unimportant as long as it
         * establishes a total order.  Comparing as integers gives us
         * that.
         */
        if (s1->suspect != s2->suspect)
                return (intptr_t)s1->suspect > (intptr_t)s2->suspect ? 1 : -1;
        if (s1->s_lno == s2->s_lno)
                return 0;
        return s1->s_lno > s2->s_lno ? 1 : -1;
}

static struct blame_entry *blame_sort(struct blame_entry *head,
                                      int (*compare_fn)(const void *, const void *))
{
        return llist_mergesort (head, get_next_blame, set_next_blame, compare_fn);
}

static int compare_commits_by_reverse_commit_date(const void *a,
                                                  const void *b,
                                                  void *c)
{
        return -compare_commits_by_commit_date(a, b, c);
}

/*
 * The current state of the blame assignment.
 */
struct scoreboard {
        /* the final commit (i.e. where we started digging from) */
        struct commit *final;
        /* Priority queue for commits with unassigned blame records */
        struct prio_queue commits;
        struct rev_info *revs;
        const char *path;

        /*
         * The contents in the final image.
         * Used by many functions to obtain contents of the nth line,
         * indexed with scoreboard.lineno[blame_entry.lno].
         */
        const char *final_buf;
        unsigned long final_buf_size;

        /* linked list of blames */
        struct blame_entry *ent;

        /* look-up a line in the final buffer */
        int num_lines;
        int *lineno;
};

static void sanity_check_refcnt(struct scoreboard *);

/*
 * If two blame entries that are next to each other came from
 * contiguous lines in the same origin (i.e. <commit, path> pair),
 * merge them together.
 */
static void coalesce(struct scoreboard *sb)
{
        struct blame_entry *ent, *next;

        for (ent = sb->ent; ent && (next = ent->next); ent = next) {
                if (ent->suspect == next->suspect &&
                    ent->s_lno + ent->num_lines == next->s_lno) {
                        ent->num_lines += next->num_lines;
                        ent->next = next->next;
                        origin_decref(next->suspect);
                        free(next);
                        ent->score = 0;
                        next = ent; /* again */
                }
        }

        if (DEBUG) /* sanity */
                sanity_check_refcnt(sb);
}

/*
 * Merge the given sorted list of blames into a preexisting origin.
 * If there were no previous blames to that commit, it is entered into
 * the commit priority queue of the score board.
 */

static void queue_blames(struct scoreboard *sb, struct origin *porigin,
                         struct blame_entry *sorted)
{
        if (porigin->suspects)
                porigin->suspects = blame_merge(porigin->suspects, sorted);
        else {
                struct origin *o;
                for (o = porigin->commit->util; o; o = o->next) {
                        if (o->suspects) {
                                porigin->suspects = sorted;
                                return;
                        }
                }
                porigin->suspects = sorted;
                prio_queue_put(&sb->commits, porigin->commit);
        }
}

/*
 * Given a commit and a path in it, create a new origin structure.
 * The callers that add blame to the scoreboard should use
 * get_origin() to obtain shared, refcounted copy instead of calling
 * this function directly.
 */
static struct origin *make_origin(struct commit *commit, const char *path)
{
        struct origin *o;
        FLEX_ALLOC_STR(o, path, path);
        o->commit = commit;
        o->refcnt = 1;
        o->next = commit->util;
        commit->util = o;
        return o;
}

/*
 * Locate an existing origin or create a new one.
 * This moves the origin to front position in the commit util list.
 */
static struct origin *get_origin(struct scoreboard *sb,
                                 struct commit *commit,
                                 const char *path)
{
        struct origin *o, *l;

        for (o = commit->util, l = NULL; o; l = o, o = o->next) {
                if (!strcmp(o->path, path)) {
                        /* bump to front */
                        if (l) {
                                l->next = o->next;
                                o->next = commit->util;
                                commit->util = o;
                        }
                        return origin_incref(o);
                }
        }
        return make_origin(commit, path);
}

/*
 * Fill the blob_sha1 field of an origin if it hasn't, so that later
 * call to fill_origin_blob() can use it to locate the data.  blob_sha1
 * for an origin is also used to pass the blame for the entire file to
 * the parent to detect the case where a child's blob is identical to
 * that of its parent's.
 *
 * This also fills origin->mode for corresponding tree path.
 */
static int fill_blob_sha1_and_mode(struct origin *origin)
{
        if (!is_null_oid(&origin->blob_oid))
                return 0;
        if (get_tree_entry(origin->commit->object.oid.hash,
                           origin->path,
                           origin->blob_oid.hash, &origin->mode))
                goto error_out;
        if (sha1_object_info(origin->blob_oid.hash, NULL) != OBJ_BLOB)
                goto error_out;
        return 0;
 error_out:
        oidclr(&origin->blob_oid);
        origin->mode = S_IFINVALID;
        return -1;
}

/*
 * We have an origin -- check if the same path exists in the
 * parent and return an origin structure to represent it.
 */
static struct origin *find_origin(struct scoreboard *sb,
                                  struct commit *parent,
                                  struct origin *origin)
{
        struct origin *porigin;
        struct diff_options diff_opts;
        const char *paths[2];

        /* First check any existing origins */
        for (porigin = parent->util; porigin; porigin = porigin->next)
                if (!strcmp(porigin->path, origin->path)) {
                        /*
                         * The same path between origin and its parent
                         * without renaming -- the most common case.
                         */
                        return origin_incref (porigin);
                }

        /* See if the origin->path is different between parent
         * and origin first.  Most of the time they are the
         * same and diff-tree is fairly efficient about this.
         */
        diff_setup(&diff_opts);
        DIFF_OPT_SET(&diff_opts, RECURSIVE);
        diff_opts.detect_rename = 0;
        diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
        paths[0] = origin->path;
        paths[1] = NULL;

        parse_pathspec(&diff_opts.pathspec,
                       PATHSPEC_ALL_MAGIC & ~PATHSPEC_LITERAL,
                       PATHSPEC_LITERAL_PATH, "", paths);
        diff_setup_done(&diff_opts);

        if (is_null_oid(&origin->commit->object.oid))
                do_diff_cache(parent->tree->object.oid.hash, &diff_opts);
        else
                diff_tree_sha1(parent->tree->object.oid.hash,
                               origin->commit->tree->object.oid.hash,
                               "", &diff_opts);
        diffcore_std(&diff_opts);

        if (!diff_queued_diff.nr) {
                /* The path is the same as parent */
                porigin = get_origin(sb, parent, origin->path);
                oidcpy(&porigin->blob_oid, &origin->blob_oid);
                porigin->mode = origin->mode;
        } else {
                /*
                 * Since origin->path is a pathspec, if the parent
                 * commit had it as a directory, we will see a whole
                 * bunch of deletion of files in the directory that we
                 * do not care about.
                 */
                int i;
                struct diff_filepair *p = NULL;
                for (i = 0; i < diff_queued_diff.nr; i++) {
                        const char *name;
                        p = diff_queued_diff.queue[i];
                        name = p->one->path ? p->one->path : p->two->path;
                        if (!strcmp(name, origin->path))
                                break;
                }
                if (!p)
                        die("internal error in blame::find_origin");
                switch (p->status) {
                default:
                        die("internal error in blame::find_origin (%c)",
                            p->status);
                case 'M':
                        porigin = get_origin(sb, parent, origin->path);
                        oidcpy(&porigin->blob_oid, &p->one->oid);
                        porigin->mode = p->one->mode;
                        break;
                case 'A':
                case 'T':
                        /* Did not exist in parent, or type changed */
                        break;
                }
        }
        diff_flush(&diff_opts);
        clear_pathspec(&diff_opts.pathspec);
        return porigin;
}

/*
 * We have an origin -- find the path that corresponds to it in its
 * parent and return an origin structure to represent it.
 */
static struct origin *find_rename(struct scoreboard *sb,
                                  struct commit *parent,
                                  struct origin *origin)
{
        struct origin *porigin = NULL;
        struct diff_options diff_opts;
        int i;

        diff_setup(&diff_opts);
        DIFF_OPT_SET(&diff_opts, RECURSIVE);
        diff_opts.detect_rename = DIFF_DETECT_RENAME;
        diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
        diff_opts.single_follow = origin->path;
        diff_setup_done(&diff_opts);

        if (is_null_oid(&origin->commit->object.oid))
                do_diff_cache(parent->tree->object.oid.hash, &diff_opts);
        else
                diff_tree_sha1(parent->tree->object.oid.hash,
                               origin->commit->tree->object.oid.hash,
                               "", &diff_opts);
        diffcore_std(&diff_opts);

        for (i = 0; i < diff_queued_diff.nr; i++) {
                struct diff_filepair *p = diff_queued_diff.queue[i];
                if ((p->status == 'R' || p->status == 'C') &&
                    !strcmp(p->two->path, origin->path)) {
                        porigin = get_origin(sb, parent, p->one->path);
                        oidcpy(&porigin->blob_oid, &p->one->oid);
                        porigin->mode = p->one->mode;
                        break;
                }
        }
        diff_flush(&diff_opts);
        clear_pathspec(&diff_opts.pathspec);
        return porigin;
}

/*
 * Append a new blame entry to a given output queue.
 */
static void add_blame_entry(struct blame_entry ***queue,
                            const struct blame_entry *src)
{
        struct blame_entry *e = xmalloc(sizeof(*e));
        memcpy(e, src, sizeof(*e));
        origin_incref(e->suspect);

        e->next = **queue;
        **queue = e;
        *queue = &e->next;
}

/*
 * src typically is on-stack; we want to copy the information in it to
 * a malloced blame_entry that gets added to the given queue.  The
 * origin of dst loses a refcnt.
 */
static void dup_entry(struct blame_entry ***queue,
                      struct blame_entry *dst, struct blame_entry *src)
{
        origin_incref(src->suspect);
        origin_decref(dst->suspect);
        memcpy(dst, src, sizeof(*src));
        dst->next = **queue;
        **queue = dst;
        *queue = &dst->next;
}

static const char *nth_line(struct scoreboard *sb, long lno)
{
        return sb->final_buf + sb->lineno[lno];
}

static const char *nth_line_cb(void *data, long lno)
{
        return nth_line((struct scoreboard *)data, lno);
}

/*
 * It is known that lines between tlno to same came from parent, and e
 * has an overlap with that range.  it also is known that parent's
 * line plno corresponds to e's line tlno.
 *
 *                <---- e ----->
 *                   <------>
 *                   <------------>
 *             <------------>
 *             <------------------>
 *
 * Split e into potentially three parts; before this chunk, the chunk
 * to be blamed for the parent, and after that portion.
 */
static void split_overlap(struct blame_entry *split,
                          struct blame_entry *e,
                          int tlno, int plno, int same,
                          struct origin *parent)
{
        int chunk_end_lno;
        memset(split, 0, sizeof(struct blame_entry [3]));

        if (e->s_lno < tlno) {
                /* there is a pre-chunk part not blamed on parent */
                split[0].suspect = origin_incref(e->suspect);
                split[0].lno = e->lno;
                split[0].s_lno = e->s_lno;
                split[0].num_lines = tlno - e->s_lno;
                split[1].lno = e->lno + tlno - e->s_lno;
                split[1].s_lno = plno;
        }
        else {
                split[1].lno = e->lno;
                split[1].s_lno = plno + (e->s_lno - tlno);
        }

        if (same < e->s_lno + e->num_lines) {
                /* there is a post-chunk part not blamed on parent */
                split[2].suspect = origin_incref(e->suspect);
                split[2].lno = e->lno + (same - e->s_lno);
                split[2].s_lno = e->s_lno + (same - e->s_lno);
                split[2].num_lines = e->s_lno + e->num_lines - same;
                chunk_end_lno = split[2].lno;
        }
        else
                chunk_end_lno = e->lno + e->num_lines;
        split[1].num_lines = chunk_end_lno - split[1].lno;

        /*
         * if it turns out there is nothing to blame the parent for,
         * forget about the splitting.  !split[1].suspect signals this.
         */
        if (split[1].num_lines < 1)
                return;
        split[1].suspect = origin_incref(parent);
}

/*
 * split_overlap() divided an existing blame e into up to three parts
 * in split.  Any assigned blame is moved to queue to
 * reflect the split.
 */
static void split_blame(struct blame_entry ***blamed,
                        struct blame_entry ***unblamed,
                        struct blame_entry *split,
                        struct blame_entry *e)
{
        if (split[0].suspect && split[2].suspect) {
                /* The first part (reuse storage for the existing entry e) */
                dup_entry(unblamed, e, &split[0]);

                /* The last part -- me */
                add_blame_entry(unblamed, &split[2]);

                /* ... and the middle part -- parent */
                add_blame_entry(blamed, &split[1]);
        }
        else if (!split[0].suspect && !split[2].suspect)
                /*
                 * The parent covers the entire area; reuse storage for
                 * e and replace it with the parent.
                 */
                dup_entry(blamed, e, &split[1]);
        else if (split[0].suspect) {
                /* me and then parent */
                dup_entry(unblamed, e, &split[0]);
                add_blame_entry(blamed, &split[1]);
        }
        else {
                /* parent and then me */
                dup_entry(blamed, e, &split[1]);
                add_blame_entry(unblamed, &split[2]);
        }
}

/*
 * After splitting the blame, the origins used by the
 * on-stack blame_entry should lose one refcnt each.
 */
static void decref_split(struct blame_entry *split)
{
        int i;

        for (i = 0; i < 3; i++)
                origin_decref(split[i].suspect);
}

/*
 * reverse_blame reverses the list given in head, appending tail.
 * That allows us to build lists in reverse order, then reverse them
 * afterwards.  This can be faster than building the list in proper
 * order right away.  The reason is that building in proper order
 * requires writing a link in the _previous_ element, while building
 * in reverse order just requires placing the list head into the
 * _current_ element.
 */

static struct blame_entry *reverse_blame(struct blame_entry *head,
                                         struct blame_entry *tail)
{
        while (head) {
                struct blame_entry *next = head->next;
                head->next = tail;
                tail = head;
                head = next;
        }
        return tail;
}

/*
 * Process one hunk from the patch between the current suspect for
 * blame_entry e and its parent.  This first blames any unfinished
 * entries before the chunk (which is where target and parent start
 * differing) on the parent, and then splits blame entries at the
 * start and at the end of the difference region.  Since use of -M and
 * -C options may lead to overlapping/duplicate source line number
 * ranges, all we can rely on from sorting/merging is the order of the
 * first suspect line number.
 */
static void blame_chunk(struct blame_entry ***dstq, struct blame_entry ***srcq,
                        int tlno, int offset, int same,
                        struct origin *parent)
{
        struct blame_entry *e = **srcq;
        struct blame_entry *samep = NULL, *diffp = NULL;

        while (e && e->s_lno < tlno) {
                struct blame_entry *next = e->next;
                /*
                 * current record starts before differing portion.  If
                 * it reaches into it, we need to split it up and
                 * examine the second part separately.
                 */
                if (e->s_lno + e->num_lines > tlno) {
                        /* Move second half to a new record */
                        int len = tlno - e->s_lno;
                        struct blame_entry *n = xcalloc(1, sizeof (struct blame_entry));
                        n->suspect = e->suspect;
                        n->lno = e->lno + len;
                        n->s_lno = e->s_lno + len;
                        n->num_lines = e->num_lines - len;
                        e->num_lines = len;
                        e->score = 0;
                        /* Push new record to diffp */
                        n->next = diffp;
                        diffp = n;
                } else
                        origin_decref(e->suspect);
                /* Pass blame for everything before the differing
                 * chunk to the parent */
                e->suspect = origin_incref(parent);
                e->s_lno += offset;
                e->next = samep;
                samep = e;
                e = next;
        }
        /*
         * As we don't know how much of a common stretch after this
         * diff will occur, the currently blamed parts are all that we
         * can assign to the parent for now.
         */

        if (samep) {
                **dstq = reverse_blame(samep, **dstq);
                *dstq = &samep->next;
        }
        /*
         * Prepend the split off portions: everything after e starts
         * after the blameable portion.
         */
        e = reverse_blame(diffp, e);

        /*
         * Now retain records on the target while parts are different
         * from the parent.
         */
        samep = NULL;
        diffp = NULL;
        while (e && e->s_lno < same) {
                struct blame_entry *next = e->next;

                /*
                 * If current record extends into sameness, need to split.
                 */
                if (e->s_lno + e->num_lines > same) {
                        /*
                         * Move second half to a new record to be
                         * processed by later chunks
                         */
                        int len = same - e->s_lno;
                        struct blame_entry *n = xcalloc(1, sizeof (struct blame_entry));
                        n->suspect = origin_incref(e->suspect);
                        n->lno = e->lno + len;
                        n->s_lno = e->s_lno + len;
                        n->num_lines = e->num_lines - len;
                        e->num_lines = len;
                        e->score = 0;
                        /* Push new record to samep */
                        n->next = samep;
                        samep = n;
                }
                e->next = diffp;
                diffp = e;
                e = next;
        }
        **srcq = reverse_blame(diffp, reverse_blame(samep, e));
        /* Move across elements that are in the unblamable portion */
        if (diffp)
                *srcq = &diffp->next;
}

struct blame_chunk_cb_data {
        struct origin *parent;
        long offset;
        struct blame_entry **dstq;
        struct blame_entry **srcq;
};

/* diff chunks are from parent to target */
static int blame_chunk_cb(long start_a, long count_a,
                          long start_b, long count_b, void *data)
{
        struct blame_chunk_cb_data *d = data;
        if (start_a - start_b != d->offset)
                die("internal error in blame::blame_chunk_cb");
        blame_chunk(&d->dstq, &d->srcq, start_b, start_a - start_b,
                    start_b + count_b, d->parent);
        d->offset = start_a + count_a - (start_b + count_b);
        return 0;
}

/*
 * We are looking at the origin 'target' and aiming to pass blame
 * for the lines it is suspected to its parent.  Run diff to find
 * which lines came from parent and pass blame for them.
 */
static void pass_blame_to_parent(struct scoreboard *sb,
                                 struct origin *target,
                                 struct origin *parent)
{
        mmfile_t file_p, file_o;
        struct blame_chunk_cb_data d;
        struct blame_entry *newdest = NULL;

        if (!target->suspects)
                return; /* nothing remains for this target */

        d.parent = parent;
        d.offset = 0;
        d.dstq = &newdest; d.srcq = &target->suspects;

        fill_origin_blob(&sb->revs->diffopt, parent, &file_p);
        fill_origin_blob(&sb->revs->diffopt, target, &file_o);
        num_get_patch++;

        if (diff_hunks(&file_p, &file_o, blame_chunk_cb, &d))
                die("unable to generate diff (%s -> %s)",
                    oid_to_hex(&parent->commit->object.oid),
                    oid_to_hex(&target->commit->object.oid));
        /* The rest are the same as the parent */
        blame_chunk(&d.dstq, &d.srcq, INT_MAX, d.offset, INT_MAX, parent);
        *d.dstq = NULL;
        queue_blames(sb, parent, newdest);

        return;
}

/*
 * The lines in blame_entry after splitting blames many times can become
 * very small and trivial, and at some point it becomes pointless to
 * blame the parents.  E.g. "\t\t}\n\t}\n\n" appears everywhere in any
 * ordinary C program, and it is not worth to say it was copied from
 * totally unrelated file in the parent.
 *
 * Compute how trivial the lines in the blame_entry are.
 */
static unsigned ent_score(struct scoreboard *sb, struct blame_entry *e)
{
        unsigned score;
        const char *cp, *ep;

        if (e->score)
                return e->score;

        score = 1;
        cp = nth_line(sb, e->lno);
        ep = nth_line(sb, e->lno + e->num_lines);
        while (cp < ep) {
                unsigned ch = *((unsigned char *)cp);
                if (isalnum(ch))
                        score++;
                cp++;
        }
        e->score = score;
        return score;
}

/*
 * best_so_far[] and this[] are both a split of an existing blame_entry
 * that passes blame to the parent.  Maintain best_so_far the best split
 * so far, by comparing this and best_so_far and copying this into
 * bst_so_far as needed.
 */
static void copy_split_if_better(struct scoreboard *sb,
                                 struct blame_entry *best_so_far,
                                 struct blame_entry *this)
{
        int i;

        if (!this[1].suspect)
                return;
        if (best_so_far[1].suspect) {
                if (ent_score(sb, &this[1]) < ent_score(sb, &best_so_far[1]))
                        return;
        }

        for (i = 0; i < 3; i++)
                origin_incref(this[i].suspect);
        decref_split(best_so_far);
        memcpy(best_so_far, this, sizeof(struct blame_entry [3]));
}

/*
 * We are looking at a part of the final image represented by
 * ent (tlno and same are offset by ent->s_lno).
 * tlno is where we are looking at in the final image.
 * up to (but not including) same match preimage.
 * plno is where we are looking at in the preimage.
 *
 * <-------------- final image ---------------------->
 *       <------ent------>
 *         ^tlno ^same
 *    <---------preimage----->
 *         ^plno
 *
 * All line numbers are 0-based.
 */
static void handle_split(struct scoreboard *sb,
                         struct blame_entry *ent,
                         int tlno, int plno, int same,
                         struct origin *parent,
                         struct blame_entry *split)
{
        if (ent->num_lines <= tlno)
                return;
        if (tlno < same) {
                struct blame_entry this[3];
                tlno += ent->s_lno;
                same += ent->s_lno;
                split_overlap(this, ent, tlno, plno, same, parent);
                copy_split_if_better(sb, split, this);
                decref_split(this);
        }
}

struct handle_split_cb_data {
        struct scoreboard *sb;
        struct blame_entry *ent;
        struct origin *parent;
        struct blame_entry *split;
        long plno;
        long tlno;
};

static int handle_split_cb(long start_a, long count_a,
                           long start_b, long count_b, void *data)
{
        struct handle_split_cb_data *d = data;
        handle_split(d->sb, d->ent, d->tlno, d->plno, start_b, d->parent,
                     d->split);
        d->plno = start_a + count_a;
        d->tlno = start_b + count_b;
        return 0;
}

/*
 * Find the lines from parent that are the same as ent so that
 * we can pass blames to it.  file_p has the blob contents for
 * the parent.
 */
static void find_copy_in_blob(struct scoreboard *sb,
                              struct blame_entry *ent,
                              struct origin *parent,
                              struct blame_entry *split,
                              mmfile_t *file_p)
{
        const char *cp;
        mmfile_t file_o;
        struct handle_split_cb_data d;

        memset(&d, 0, sizeof(d));
        d.sb = sb; d.ent = ent; d.parent = parent; d.split = split;
        /*
         * Prepare mmfile that contains only the lines in ent.
         */
        cp = nth_line(sb, ent->lno);
        file_o.ptr = (char *) cp;
        file_o.size = nth_line(sb, ent->lno + ent->num_lines) - cp;

        /*
         * file_o is a part of final image we are annotating.
         * file_p partially may match that image.
         */
        memset(split, 0, sizeof(struct blame_entry [3]));
        if (diff_hunks(file_p, &file_o, handle_split_cb, &d))
                die("unable to generate diff (%s)",
                    oid_to_hex(&parent->commit->object.oid));
        /* remainder, if any, all match the preimage */
        handle_split(sb, ent, d.tlno, d.plno, ent->num_lines, parent, split);
}

/* Move all blame entries from list *source that have a score smaller
 * than score_min to the front of list *small.
 * Returns a pointer to the link pointing to the old head of the small list.
 */

static struct blame_entry **filter_small(struct scoreboard *sb,
                                         struct blame_entry **small,
                                         struct blame_entry **source,
                                         unsigned score_min)
{
        struct blame_entry *p = *source;
        struct blame_entry *oldsmall = *small;
        while (p) {
                if (ent_score(sb, p) <= score_min) {
                        *small = p;
                        small = &p->next;
                        p = *small;
                } else {
                        *source = p;
                        source = &p->next;
                        p = *source;
                }
        }
        *small = oldsmall;
        *source = NULL;
        return small;
}

/*
 * See if lines currently target is suspected for can be attributed to
 * parent.
 */
static void find_move_in_parent(struct scoreboard *sb,
                                struct blame_entry ***blamed,
                                struct blame_entry **toosmall,
                                struct origin *target,
                                struct origin *parent)
{
        struct blame_entry *e, split[3];
        struct blame_entry *unblamed = target->suspects;
        struct blame_entry *leftover = NULL;
        mmfile_t file_p;

        if (!unblamed)
                return; /* nothing remains for this target */

        fill_origin_blob(&sb->revs->diffopt, parent, &file_p);
        if (!file_p.ptr)
                return;

        /* At each iteration, unblamed has a NULL-terminated list of
         * entries that have not yet been tested for blame.  leftover
         * contains the reversed list of entries that have been tested
         * without being assignable to the parent.
         */
        do {
                struct blame_entry **unblamedtail = &unblamed;
                struct blame_entry *next;
                for (e = unblamed; e; e = next) {
                        next = e->next;
                        find_copy_in_blob(sb, e, parent, split, &file_p);
                        if (split[1].suspect &&
                            blame_move_score < ent_score(sb, &split[1])) {
                                split_blame(blamed, &unblamedtail, split, e);
                        } else {
                                e->next = leftover;
                                leftover = e;
                        }
                        decref_split(split);
                }
                *unblamedtail = NULL;
                toosmall = filter_small(sb, toosmall, &unblamed, blame_move_score);
        } while (unblamed);
        target->suspects = reverse_blame(leftover, NULL);
}

struct blame_list {
        struct blame_entry *ent;
        struct blame_entry split[3];
};

/*
 * Count the number of entries the target is suspected for,
 * and prepare a list of entry and the best split.
 */
static struct blame_list *setup_blame_list(struct blame_entry *unblamed,
                                           int *num_ents_p)
{
        struct blame_entry *e;
        int num_ents, i;
        struct blame_list *blame_list = NULL;

        for (e = unblamed, num_ents = 0; e; e = e->next)
                num_ents++;
        if (num_ents) {
                blame_list = xcalloc(num_ents, sizeof(struct blame_list));
                for (e = unblamed, i = 0; e; e = e->next)
                        blame_list[i++].ent = e;
        }
        *num_ents_p = num_ents;
        return blame_list;
}

/*
 * For lines target is suspected for, see if we can find code movement
 * across file boundary from the parent commit.  porigin is the path
 * in the parent we already tried.
 */
static void find_copy_in_parent(struct scoreboard *sb,
                                struct blame_entry ***blamed,
                                struct blame_entry **toosmall,
                                struct origin *target,
                                struct commit *parent,
                                struct origin *porigin,
                                int opt)
{
        struct diff_options diff_opts;
        int i, j;
        struct blame_list *blame_list;
        int num_ents;
        struct blame_entry *unblamed = target->suspects;
        struct blame_entry *leftover = NULL;

        if (!unblamed)
                return; /* nothing remains for this target */

        diff_setup(&diff_opts);
        DIFF_OPT_SET(&diff_opts, RECURSIVE);
        diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;

        diff_setup_done(&diff_opts);

        /* Try "find copies harder" on new path if requested;
         * we do not want to use diffcore_rename() actually to
         * match things up; find_copies_harder is set only to
         * force diff_tree_sha1() to feed all filepairs to diff_queue,
         * and this code needs to be after diff_setup_done(), which
         * usually makes find-copies-harder imply copy detection.
         */
        if ((opt & PICKAXE_BLAME_COPY_HARDEST)
            || ((opt & PICKAXE_BLAME_COPY_HARDER)
                && (!porigin || strcmp(target->path, porigin->path))))
                DIFF_OPT_SET(&diff_opts, FIND_COPIES_HARDER);

        if (is_null_oid(&target->commit->object.oid))
                do_diff_cache(parent->tree->object.oid.hash, &diff_opts);
        else
                diff_tree_sha1(parent->tree->object.oid.hash,
                               target->commit->tree->object.oid.hash,
                               "", &diff_opts);

        if (!DIFF_OPT_TST(&diff_opts, FIND_COPIES_HARDER))
                diffcore_std(&diff_opts);

        do {
                struct blame_entry **unblamedtail = &unblamed;
                blame_list = setup_blame_list(unblamed, &num_ents);

                for (i = 0; i < diff_queued_diff.nr; i++) {
                        struct diff_filepair *p = diff_queued_diff.queue[i];
                        struct origin *norigin;
                        mmfile_t file_p;
                        struct blame_entry this[3];

                        if (!DIFF_FILE_VALID(p->one))
                                continue; /* does not exist in parent */
                        if (S_ISGITLINK(p->one->mode))
                                continue; /* ignore git links */
                        if (porigin && !strcmp(p->one->path, porigin->path))
                                /* find_move already dealt with this path */
                                continue;

                        norigin = get_origin(sb, parent, p->one->path);
                        oidcpy(&norigin->blob_oid, &p->one->oid);
                        norigin->mode = p->one->mode;
                        fill_origin_blob(&sb->revs->diffopt, norigin, &file_p);
                        if (!file_p.ptr)
                                continue;

                        for (j = 0; j < num_ents; j++) {
                                find_copy_in_blob(sb, blame_list[j].ent,
                                                  norigin, this, &file_p);
                                copy_split_if_better(sb, blame_list[j].split,
                                                     this);
                                decref_split(this);
                        }
                        origin_decref(norigin);
                }

                for (j = 0; j < num_ents; j++) {
                        struct blame_entry *split = blame_list[j].split;
                        if (split[1].suspect &&
                            blame_copy_score < ent_score(sb, &split[1])) {
                                split_blame(blamed, &unblamedtail, split,
                                            blame_list[j].ent);
                        } else {
                                blame_list[j].ent->next = leftover;
                                leftover = blame_list[j].ent;
                        }
                        decref_split(split);
                }
                free(blame_list);
                *unblamedtail = NULL;
                toosmall = filter_small(sb, toosmall, &unblamed, blame_copy_score);
        } while (unblamed);
        target->suspects = reverse_blame(leftover, NULL);
        diff_flush(&diff_opts);
        clear_pathspec(&diff_opts.pathspec);
}

/*
 * The blobs of origin and porigin exactly match, so everything
 * origin is suspected for can be blamed on the parent.
 */
static void pass_whole_blame(struct scoreboard *sb,
                             struct origin *origin, struct origin *porigin)
{
        struct blame_entry *e, *suspects;

        if (!porigin->file.ptr && origin->file.ptr) {
                /* Steal its file */
                porigin->file = origin->file;
                origin->file.ptr = NULL;
        }
        suspects = origin->suspects;
        origin->suspects = NULL;
        for (e = suspects; e; e = e->next) {
                origin_incref(porigin);
                origin_decref(e->suspect);
                e->suspect = porigin;
        }
        queue_blames(sb, porigin, suspects);
}

/*
 * We pass blame from the current commit to its parents.  We keep saying
 * "parent" (and "porigin"), but what we mean is to find scapegoat to
 * exonerate ourselves.
 */
static struct commit_list *first_scapegoat(struct rev_info *revs, struct commit *commit)
{
        if (!reverse) {
                if (revs->first_parent_only &&
                    commit->parents &&
                    commit->parents->next) {
                        free_commit_list(commit->parents->next);
                        commit->parents->next = NULL;
                }
                return commit->parents;
        }
        return lookup_decoration(&revs->children, &commit->object);
}

static int num_scapegoats(struct rev_info *revs, struct commit *commit)
{
        struct commit_list *l = first_scapegoat(revs, commit);
        return commit_list_count(l);
}

/* Distribute collected unsorted blames to the respected sorted lists
 * in the various origins.
 */
static void distribute_blame(struct scoreboard *sb, struct blame_entry *blamed)
{
        blamed = blame_sort(blamed, compare_blame_suspect);
        while (blamed)
        {
                struct origin *porigin = blamed->suspect;
                struct blame_entry *suspects = NULL;
                do {
                        struct blame_entry *next = blamed->next;
                        blamed->next = suspects;
                        suspects = blamed;
                        blamed = next;
                } while (blamed && blamed->suspect == porigin);
                suspects = reverse_blame(suspects, NULL);
                queue_blames(sb, porigin, suspects);
        }
}

#define MAXSG 16

static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
{
        struct rev_info *revs = sb->revs;
        int i, pass, num_sg;
        struct commit *commit = origin->commit;
        struct commit_list *sg;
        struct origin *sg_buf[MAXSG];
        struct origin *porigin, **sg_origin = sg_buf;
        struct blame_entry *toosmall = NULL;
        struct blame_entry *blames, **blametail = &blames;

        num_sg = num_scapegoats(revs, commit);
        if (!num_sg)
                goto finish;
        else if (num_sg < ARRAY_SIZE(sg_buf))
                memset(sg_buf, 0, sizeof(sg_buf));
        else
                sg_origin = xcalloc(num_sg, sizeof(*sg_origin));

        /*
         * The first pass looks for unrenamed path to optimize for
         * common cases, then we look for renames in the second pass.
         */
        for (pass = 0; pass < 2 - no_whole_file_rename; pass++) {
                struct origin *(*find)(struct scoreboard *,
                                       struct commit *, struct origin *);
                find = pass ? find_rename : find_origin;

                for (i = 0, sg = first_scapegoat(revs, commit);
                     i < num_sg && sg;
                     sg = sg->next, i++) {
                        struct commit *p = sg->item;
                        int j, same;

                        if (sg_origin[i])
                                continue;
                        if (parse_commit(p))
                                continue;
                        porigin = find(sb, p, origin);
                        if (!porigin)
                                continue;
                        if (!oidcmp(&porigin->blob_oid, &origin->blob_oid)) {
                                pass_whole_blame(sb, origin, porigin);
                                origin_decref(porigin);
                                goto finish;
                        }
                        for (j = same = 0; j < i; j++)
                                if (sg_origin[j] &&
                                    !oidcmp(&sg_origin[j]->blob_oid, &porigin->blob_oid)) {
                                        same = 1;
                                        break;
                                }
                        if (!same)
                                sg_origin[i] = porigin;
                        else
                                origin_decref(porigin);
                }
        }

        num_commits++;
        for (i = 0, sg = first_scapegoat(revs, commit);
             i < num_sg && sg;
             sg = sg->next, i++) {
                struct origin *porigin = sg_origin[i];
                if (!porigin)
                        continue;
                if (!origin->previous) {
                        origin_incref(porigin);
                        origin->previous = porigin;
                }
                pass_blame_to_parent(sb, origin, porigin);
                if (!origin->suspects)
                        goto finish;
        }

        /*
         * Optionally find moves in parents' files.
         */
        if (opt & PICKAXE_BLAME_MOVE) {
                filter_small(sb, &toosmall, &origin->suspects, blame_move_score);
                if (origin->suspects) {
                        for (i = 0, sg = first_scapegoat(revs, commit);
                             i < num_sg && sg;
                             sg = sg->next, i++) {
                                struct origin *porigin = sg_origin[i];
                                if (!porigin)
                                        continue;
                                find_move_in_parent(sb, &blametail, &toosmall, origin, porigin);
                                if (!origin->suspects)
                                        break;
                        }
                }
        }

        /*
         * Optionally find copies from parents' files.
         */
        if (opt & PICKAXE_BLAME_COPY) {
                if (blame_copy_score > blame_move_score)
                        filter_small(sb, &toosmall, &origin->suspects, blame_copy_score);
                else if (blame_copy_score < blame_move_score) {
                        origin->suspects = blame_merge(origin->suspects, toosmall);
                        toosmall = NULL;
                        filter_small(sb, &toosmall, &origin->suspects, blame_copy_score);
                }
                if (!origin->suspects)
                        goto finish;

                for (i = 0, sg = first_scapegoat(revs, commit);
                     i < num_sg && sg;
                     sg = sg->next, i++) {
                        struct origin *porigin = sg_origin[i];
                        find_copy_in_parent(sb, &blametail, &toosmall,
                                            origin, sg->item, porigin, opt);
                        if (!origin->suspects)
                                goto finish;
                }
        }

finish:
        *blametail = NULL;
        distribute_blame(sb, blames);
        /*
         * prepend toosmall to origin->suspects
         *
         * There is no point in sorting: this ends up on a big
         * unsorted list in the caller anyway.
         */
        if (toosmall) {
                struct blame_entry **tail = &toosmall;
                while (*tail)
                        tail = &(*tail)->next;
                *tail = origin->suspects;
                origin->suspects = toosmall;
        }
        for (i = 0; i < num_sg; i++) {
                if (sg_origin[i]) {
                        drop_origin_blob(sg_origin[i]);
                        origin_decref(sg_origin[i]);
                }
        }
        drop_origin_blob(origin);
        if (sg_buf != sg_origin)
                free(sg_origin);
}

/*
 * Information on commits, used for output.
 */
struct commit_info {
        struct strbuf author;
        struct strbuf author_mail;
        unsigned long author_time;
        struct strbuf author_tz;

        /* filled only when asked for details */
        struct strbuf committer;
        struct strbuf committer_mail;
        unsigned long committer_time;
        struct strbuf committer_tz;

        struct strbuf summary;
};

/*
 * Parse author/committer line in the commit object buffer
 */
static void get_ac_line(const char *inbuf, const char *what,
        struct strbuf *name, struct strbuf *mail,
        unsigned long *time, struct strbuf *tz)
{
        struct ident_split ident;
        size_t len, maillen, namelen;
        char *tmp, *endp;
        const char *namebuf, *mailbuf;

        tmp = strstr(inbuf, what);
        if (!tmp)
                goto error_out;
        tmp += strlen(what);
        endp = strchr(tmp, '\n');
        if (!endp)
                len = strlen(tmp);
        else
                len = endp - tmp;

        if (split_ident_line(&ident, tmp, len)) {
        error_out:
                /* Ugh */
                tmp = "(unknown)";
                strbuf_addstr(name, tmp);
                strbuf_addstr(mail, tmp);
                strbuf_addstr(tz, tmp);
                *time = 0;
                return;
        }

        namelen = ident.name_end - ident.name_begin;
        namebuf = ident.name_begin;

        maillen = ident.mail_end - ident.mail_begin;
        mailbuf = ident.mail_begin;

        if (ident.date_begin && ident.date_end)
                *time = strtoul(ident.date_begin, NULL, 10);
        else
                *time = 0;

        if (ident.tz_begin && ident.tz_end)
                strbuf_add(tz, ident.tz_begin, ident.tz_end - ident.tz_begin);
        else
                strbuf_addstr(tz, "(unknown)");

        /*
         * Now, convert both name and e-mail using mailmap
         */
        map_user(&mailmap, &mailbuf, &maillen,
                 &namebuf, &namelen);

        strbuf_addf(mail, "<%.*s>", (int)maillen, mailbuf);
        strbuf_add(name, namebuf, namelen);
}

static void commit_info_init(struct commit_info *ci)
{

        strbuf_init(&ci->author, 0);
        strbuf_init(&ci->author_mail, 0);
        strbuf_init(&ci->author_tz, 0);
        strbuf_init(&ci->committer, 0);
        strbuf_init(&ci->committer_mail, 0);
        strbuf_init(&ci->committer_tz, 0);
        strbuf_init(&ci->summary, 0);
}

static void commit_info_destroy(struct commit_info *ci)
{

        strbuf_release(&ci->author);
        strbuf_release(&ci->author_mail);
        strbuf_release(&ci->author_tz);
        strbuf_release(&ci->committer);
        strbuf_release(&ci->committer_mail);
        strbuf_release(&ci->committer_tz);
        strbuf_release(&ci->summary);
}

static void get_commit_info(struct commit *commit,
                            struct commit_info *ret,
                            int detailed)
{
        int len;
        const char *subject, *encoding;
        const char *message;

        commit_info_init(ret);

        encoding = get_log_output_encoding();
        message = logmsg_reencode(commit, NULL, encoding);
        get_ac_line(message, "\nauthor ",
                    &ret->author, &ret->author_mail,
                    &ret->author_time, &ret->author_tz);

        if (!detailed) {
                unuse_commit_buffer(commit, message);
                return;
        }

        get_ac_line(message, "\ncommitter ",
                    &ret->committer, &ret->committer_mail,
                    &ret->committer_time, &ret->committer_tz);

        len = find_commit_subject(message, &subject);
        if (len)
                strbuf_add(&ret->summary, subject, len);
        else
                strbuf_addf(&ret->summary, "(%s)", oid_to_hex(&commit->object.oid));

        unuse_commit_buffer(commit, message);
}

/*
 * Write out any suspect information which depends on the path. This must be
 * handled separately from emit_one_suspect_detail(), because a given commit
 * may have changes in multiple paths. So this needs to appear each time
 * we mention a new group.
 *
 * To allow LF and other nonportable characters in pathnames,
 * they are c-style quoted as needed.
 */
static void write_filename_info(struct origin *suspect)
{
        if (suspect->previous) {
                struct origin *prev = suspect->previous;
                printf("previous %s ", oid_to_hex(&prev->commit->object.oid));
                write_name_quoted(prev->path, stdout, '\n');
        }
        printf("filename ");
        write_name_quoted(suspect->path, stdout, '\n');
}

/*
 * Porcelain/Incremental format wants to show a lot of details per
 * commit.  Instead of repeating this every line, emit it only once,
 * the first time each commit appears in the output (unless the
 * user has specifically asked for us to repeat).
 */
static int emit_one_suspect_detail(struct origin *suspect, int repeat)
{
        struct commit_info ci;

        if (!repeat && (suspect->commit->object.flags & METAINFO_SHOWN))
                return 0;

        suspect->commit->object.flags |= METAINFO_SHOWN;
        get_commit_info(suspect->commit, &ci, 1);
        printf("author %s\n", ci.author.buf);
        printf("author-mail %s\n", ci.author_mail.buf);
        printf("author-time %lu\n", ci.author_time);
        printf("author-tz %s\n", ci.author_tz.buf);
        printf("committer %s\n", ci.committer.buf);
        printf("committer-mail %s\n", ci.committer_mail.buf);
        printf("committer-time %lu\n", ci.committer_time);
        printf("committer-tz %s\n", ci.committer_tz.buf);
        printf("summary %s\n", ci.summary.buf);
        if (suspect->commit->object.flags & UNINTERESTING)
                printf("boundary\n");

        commit_info_destroy(&ci);

        return 1;
}

/*
 * The blame_entry is found to be guilty for the range.
 * Show it in incremental output.
 */
static void found_guilty_entry(struct blame_entry *ent,
                           struct progress_info *pi)
{
        if (incremental) {
                struct origin *suspect = ent->suspect;

                printf("%s %d %d %d\n",
                       oid_to_hex(&suspect->commit->object.oid),
                       ent->s_lno + 1, ent->lno + 1, ent->num_lines);
                emit_one_suspect_detail(suspect, 0);
                write_filename_info(suspect);
                maybe_flush_or_die(stdout, "stdout");
        }
        pi->blamed_lines += ent->num_lines;
        display_progress(pi->progress, pi->blamed_lines);
}

/*
 * The main loop -- while we have blobs with lines whose true origin
 * is still unknown, pick one blob, and allow its lines to pass blames
 * to its parents. */
static void assign_blame(struct scoreboard *sb, int opt)
{
        struct rev_info *revs = sb->revs;
        struct commit *commit = prio_queue_get(&sb->commits);
        struct progress_info pi = { NULL, 0 };

        if (show_progress)
                pi.progress = start_progress_delay(_("Blaming lines"),
                                                   sb->num_lines, 50, 1);

        while (commit) {
                struct blame_entry *ent;
                struct origin *suspect = commit->util;

                /* find one suspect to break down */
                while (suspect && !suspect->suspects)
                        suspect = suspect->next;

                if (!suspect) {
                        commit = prio_queue_get(&sb->commits);
                        continue;
                }

                assert(commit == suspect->commit);

                /*
                 * We will use this suspect later in the loop,
                 * so hold onto it in the meantime.
                 */
                origin_incref(suspect);
                parse_commit(commit);
                if (reverse ||
                    (!(commit->object.flags & UNINTERESTING) &&
                     !(revs->max_age != -1 && commit->date < revs->max_age)))
                        pass_blame(sb, suspect, opt);
                else {
                        commit->object.flags |= UNINTERESTING;
                        if (commit->object.parsed)
                                mark_parents_uninteresting(commit);
                }
                /* treat root commit as boundary */
                if (!commit->parents && !show_root)
                        commit->object.flags |= UNINTERESTING;

                /* Take responsibility for the remaining entries */
                ent = suspect->suspects;
                if (ent) {
                        suspect->guilty = 1;
                        for (;;) {
                                struct blame_entry *next = ent->next;
                                found_guilty_entry(ent, &pi);
                                if (next) {
                                        ent = next;
                                        continue;
                                }
                                ent->next = sb->ent;
                                sb->ent = suspect->suspects;
                                suspect->suspects = NULL;
                                break;
                        }
                }
                origin_decref(suspect);

                if (DEBUG) /* sanity */
                        sanity_check_refcnt(sb);
        }

        stop_progress(&pi.progress);
}

static const char *format_time(unsigned long time, const char *tz_str,
                               int show_raw_time)
{
        static struct strbuf time_buf = STRBUF_INIT;

        strbuf_reset(&time_buf);
        if (show_raw_time) {
                strbuf_addf(&time_buf, "%lu %s", time, tz_str);
        }
        else {
                const char *time_str;
                size_t time_width;
                int tz;
                tz = atoi(tz_str);
                time_str = show_date(time, tz, &blame_date_mode);
                strbuf_addstr(&time_buf, time_str);
                /*
                 * Add space paddings to time_buf to display a fixed width
                 * string, and use time_width for display width calibration.
                 */
                for (time_width = utf8_strwidth(time_str);
                     time_width < blame_date_width;
                     time_width++)
                        strbuf_addch(&time_buf, ' ');
        }
        return time_buf.buf;
}

#define OUTPUT_ANNOTATE_COMPAT  001
#define OUTPUT_LONG_OBJECT_NAME 002
#define OUTPUT_RAW_TIMESTAMP    004
#define OUTPUT_PORCELAIN        010
#define OUTPUT_SHOW_NAME        020
#define OUTPUT_SHOW_NUMBER      040
#define OUTPUT_SHOW_SCORE      0100
#define OUTPUT_NO_AUTHOR       0200
#define OUTPUT_SHOW_EMAIL       0400
#define OUTPUT_LINE_PORCELAIN 01000

static void emit_porcelain_details(struct origin *suspect, int repeat)
{
        if (emit_one_suspect_detail(suspect, repeat) ||
            (suspect->commit->object.flags & MORE_THAN_ONE_PATH))
                write_filename_info(suspect);
}

static void emit_porcelain(struct scoreboard *sb, struct blame_entry *ent,
                           int opt)
{
        int repeat = opt & OUTPUT_LINE_PORCELAIN;
        int cnt;
        const char *cp;
        struct origin *suspect = ent->suspect;
        char hex[GIT_SHA1_HEXSZ + 1];

        oid_to_hex_r(hex, &suspect->commit->object.oid);
        printf("%s %d %d %d\n",
               hex,
               ent->s_lno + 1,
               ent->lno + 1,
               ent->num_lines);
        emit_porcelain_details(suspect, repeat);

        cp = nth_line(sb, ent->lno);
        for (cnt = 0; cnt < ent->num_lines; cnt++) {
                char ch;
                if (cnt) {
                        printf("%s %d %d\n", hex,
                               ent->s_lno + 1 + cnt,
                               ent->lno + 1 + cnt);
                        if (repeat)
                                emit_porcelain_details(suspect, 1);
                }
                putchar('\t');
                do {
                        ch = *cp++;
                        putchar(ch);
                } while (ch != '\n' &&
                         cp < sb->final_buf + sb->final_buf_size);
        }

        if (sb->final_buf_size && cp[-1] != '\n')
                putchar('\n');
}

static void emit_other(struct scoreboard *sb, struct blame_entry *ent, int opt)
{
        int cnt;
        const char *cp;
        struct origin *suspect = ent->suspect;
        struct commit_info ci;
        char hex[GIT_SHA1_HEXSZ + 1];
        int show_raw_time = !!(opt & OUTPUT_RAW_TIMESTAMP);

        get_commit_info(suspect->commit, &ci, 1);
        oid_to_hex_r(hex, &suspect->commit->object.oid);

        cp = nth_line(sb, ent->lno);
        for (cnt = 0; cnt < ent->num_lines; cnt++) {
                char ch;
                int length = (opt & OUTPUT_LONG_OBJECT_NAME) ? GIT_SHA1_HEXSZ : abbrev;

                if (suspect->commit->object.flags & UNINTERESTING) {
                        if (blank_boundary)
                                memset(hex, ' ', length);
                        else if (!(opt & OUTPUT_ANNOTATE_COMPAT)) {
                                length--;
                                putchar('^');
                        }
                }

                printf("%.*s", length, hex);
                if (opt & OUTPUT_ANNOTATE_COMPAT) {
                        const char *name;
                        if (opt & OUTPUT_SHOW_EMAIL)
                                name = ci.author_mail.buf;
                        else
                                name = ci.author.buf;
                        printf("\t(%10s\t%10s\t%d)", name,
                               format_time(ci.author_time, ci.author_tz.buf,
                                           show_raw_time),
                               ent->lno + 1 + cnt);
                } else {
                        if (opt & OUTPUT_SHOW_SCORE)
                                printf(" %*d %02d",
                                       max_score_digits, ent->score,
                                       ent->suspect->refcnt);
                        if (opt & OUTPUT_SHOW_NAME)
                                printf(" %-*.*s", longest_file, longest_file,
                                       suspect->path);
                        if (opt & OUTPUT_SHOW_NUMBER)
                                printf(" %*d", max_orig_digits,
                                       ent->s_lno + 1 + cnt);

                        if (!(opt & OUTPUT_NO_AUTHOR)) {
                                const char *name;
                                int pad;
                                if (opt & OUTPUT_SHOW_EMAIL)
                                        name = ci.author_mail.buf;
                                else
                                        name = ci.author.buf;
                                pad = longest_author - utf8_strwidth(name);
                                printf(" (%s%*s %10s",
                                       name, pad, "",
                                       format_time(ci.author_time,
                                                   ci.author_tz.buf,
                                                   show_raw_time));
                        }
                        printf(" %*d) ",
                               max_digits, ent->lno + 1 + cnt);
                }
                do {
                        ch = *cp++;
                        putchar(ch);
                } while (ch != '\n' &&
                         cp < sb->final_buf + sb->final_buf_size);
        }

        if (sb->final_buf_size && cp[-1] != '\n')
                putchar('\n');

        commit_info_destroy(&ci);
}

static void output(struct scoreboard *sb, int option)
{
        struct blame_entry *ent;

        if (option & OUTPUT_PORCELAIN) {
                for (ent = sb->ent; ent; ent = ent->next) {
                        int count = 0;
                        struct origin *suspect;
                        struct commit *commit = ent->suspect->commit;
                        if (commit->object.flags & MORE_THAN_ONE_PATH)
                                continue;
                        for (suspect = commit->util; suspect; suspect = suspect->next) {
                                if (suspect->guilty && count++) {
                                        commit->object.flags |= MORE_THAN_ONE_PATH;
                                        break;
                                }
                        }
                }
        }

        for (ent = sb->ent; ent; ent = ent->next) {
                if (option & OUTPUT_PORCELAIN)
                        emit_porcelain(sb, ent, option);
                else {
                        emit_other(sb, ent, option);
                }
        }
}

static const char *get_next_line(const char *start, const char *end)
{
        const char *nl = memchr(start, '\n', end - start);
        return nl ? nl + 1 : end;
}

/*
 * To allow quick access to the contents of nth line in the
 * final image, prepare an index in the scoreboard.
 */
static int prepare_lines(struct scoreboard *sb)
{
        const char *buf = sb->final_buf;
        unsigned long len = sb->final_buf_size;
        const char *end = buf + len;
        const char *p;
        int *lineno;
        int num = 0;

        for (p = buf; p < end; p = get_next_line(p, end))
                num++;

        ALLOC_ARRAY(sb->lineno, num + 1);
        lineno = sb->lineno;

        for (p = buf; p < end; p = get_next_line(p, end))
                *lineno++ = p - buf;

        *lineno = len;

        sb->num_lines = num;
        return sb->num_lines;
}

/*
 * Add phony grafts for use with -S; this is primarily to
 * support git's cvsserver that wants to give a linear history
 * to its clients.
 */
static int read_ancestry(const char *graft_file)
{
        FILE *fp = fopen(graft_file, "r");
        struct strbuf buf = STRBUF_INIT;
        if (!fp)
                return -1;
        while (!strbuf_getwholeline(&buf, fp, '\n')) {
                /* The format is just "Commit Parent1 Parent2 ...\n" */
                struct commit_graft *graft = read_graft_line(buf.buf, buf.len);
                if (graft)
                        register_commit_graft(graft, 0);
        }
        fclose(fp);
        strbuf_release(&buf);
        return 0;
}

static int update_auto_abbrev(int auto_abbrev, struct origin *suspect)
{
        const char *uniq = find_unique_abbrev(suspect->commit->object.oid.hash,
                                              auto_abbrev);
        int len = strlen(uniq);
        if (auto_abbrev < len)
                return len;
        return auto_abbrev;
}

/*
 * How many columns do we need to show line numbers, authors,
 * and filenames?
 */
static void find_alignment(struct scoreboard *sb, int *option)
{
        int longest_src_lines = 0;
        int longest_dst_lines = 0;
        unsigned largest_score = 0;
        struct blame_entry *e;
        int compute_auto_abbrev = (abbrev < 0);
        int auto_abbrev = DEFAULT_ABBREV;

        for (e = sb->ent; e; e = e->next) {
                struct origin *suspect = e->suspect;
                int num;

                if (compute_auto_abbrev)
                        auto_abbrev = update_auto_abbrev(auto_abbrev, suspect);
                if (strcmp(suspect->path, sb->path))
                        *option |= OUTPUT_SHOW_NAME;
                num = strlen(suspect->path);
                if (longest_file < num)
                        longest_file = num;
                if (!(suspect->commit->object.flags & METAINFO_SHOWN)) {
                        struct commit_info ci;
                        suspect->commit->object.flags |= METAINFO_SHOWN;
                        get_commit_info(suspect->commit, &ci, 1);
                        if (*option & OUTPUT_SHOW_EMAIL)
                                num = utf8_strwidth(ci.author_mail.buf);
                        else
                                num = utf8_strwidth(ci.author.buf);
                        if (longest_author < num)
                                longest_author = num;
                        commit_info_destroy(&ci);
                }
                num = e->s_lno + e->num_lines;
                if (longest_src_lines < num)
                        longest_src_lines = num;
                num = e->lno + e->num_lines;
                if (longest_dst_lines < num)
                        longest_dst_lines = num;
                if (largest_score < ent_score(sb, e))
                        largest_score = ent_score(sb, e);
        }
        max_orig_digits = decimal_width(longest_src_lines);
        max_digits = decimal_width(longest_dst_lines);
        max_score_digits = decimal_width(largest_score);

        if (compute_auto_abbrev)
                /* one more abbrev length is needed for the boundary commit */
                abbrev = auto_abbrev + 1;
}

/*
 * For debugging -- origin is refcounted, and this asserts that
 * we do not underflow.
 */
static void sanity_check_refcnt(struct scoreboard *sb)
{
        int baa = 0;
        struct blame_entry *ent;

        for (ent = sb->ent; ent; ent = ent->next) {
                /* Nobody should have zero or negative refcnt */
                if (ent->suspect->refcnt <= 0) {
                        fprintf(stderr, "%s in %s has negative refcnt %d\n",
                                ent->suspect->path,
                                oid_to_hex(&ent->suspect->commit->object.oid),
                                ent->suspect->refcnt);
                        baa = 1;
                }
        }
        if (baa) {
                int opt = 0160;
                find_alignment(sb, &opt);
                output(sb, opt);
                die("Baa %d!", baa);
        }
}

static unsigned parse_score(const char *arg)
{
        char *end;
        unsigned long score = strtoul(arg, &end, 10);
        if (*end)
                return 0;
        return score;
}

static const char *add_prefix(const char *prefix, const char *path)
{
        return prefix_path(prefix, prefix ? strlen(prefix) : 0, path);
}

static int git_blame_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "blame.showroot")) {
                show_root = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "blame.blankboundary")) {
                blank_boundary = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "blame.showemail")) {
                int *output_option = cb;
                if (git_config_bool(var, value))
                        *output_option |= OUTPUT_SHOW_EMAIL;
                else
                        *output_option &= ~OUTPUT_SHOW_EMAIL;
                return 0;
        }
        if (!strcmp(var, "blame.date")) {
                if (!value)
                        return config_error_nonbool(var);
                parse_date_format(value, &blame_date_mode);
                return 0;
        }

        if (git_diff_heuristic_config(var, value, cb) < 0)
                return -1;
        if (userdiff_config(var, value) < 0)
                return -1;

        return git_default_config(var, value, cb);
}

static void verify_working_tree_path(struct commit *work_tree, const char *path)
{
        struct commit_list *parents;
        int pos;

        for (parents = work_tree->parents; parents; parents = parents->next) {
                const struct object_id *commit_oid = &parents->item->object.oid;
                struct object_id blob_oid;
                unsigned mode;

                if (!get_tree_entry(commit_oid->hash, path, blob_oid.hash, &mode) &&
                    sha1_object_info(blob_oid.hash, NULL) == OBJ_BLOB)
                        return;
        }

        pos = cache_name_pos(path, strlen(path));
        if (pos >= 0)
                ; /* path is in the index */
        else if (-1 - pos < active_nr &&
                 !strcmp(active_cache[-1 - pos]->name, path))
                ; /* path is in the index, unmerged */
        else
                die("no such path '%s' in HEAD", path);
}

static struct commit_list **append_parent(struct commit_list **tail, const struct object_id *oid)
{
        struct commit *parent;

        parent = lookup_commit_reference(oid->hash);
        if (!parent)
                die("no such commit %s", oid_to_hex(oid));
        return &commit_list_insert(parent, tail)->next;
}

static void append_merge_parents(struct commit_list **tail)
{
        int merge_head;
        struct strbuf line = STRBUF_INIT;

        merge_head = open(git_path_merge_head(), O_RDONLY);
        if (merge_head < 0) {
                if (errno == ENOENT)
                        return;
                die("cannot open '%s' for reading", git_path_merge_head());
        }

        while (!strbuf_getwholeline_fd(&line, merge_head, '\n')) {
                struct object_id oid;
                if (line.len < GIT_SHA1_HEXSZ || get_oid_hex(line.buf, &oid))
                        die("unknown line in '%s': %s", git_path_merge_head(), line.buf);
                tail = append_parent(tail, &oid);
        }
        close(merge_head);
        strbuf_release(&line);
}

/*
 * This isn't as simple as passing sb->buf and sb->len, because we
 * want to transfer ownership of the buffer to the commit (so we
 * must use detach).
 */
static void set_commit_buffer_from_strbuf(struct commit *c, struct strbuf *sb)
{
        size_t len;
        void *buf = strbuf_detach(sb, &len);
        set_commit_buffer(c, buf, len);
}

/*
 * Prepare a dummy commit that represents the work tree (or staged) item.
 * Note that annotating work tree item never works in the reverse.
 */
static struct commit *fake_working_tree_commit(struct diff_options *opt,
                                               const char *path,
                                               const char *contents_from)
{
        struct commit *commit;
        struct origin *origin;
        struct commit_list **parent_tail, *parent;
        struct object_id head_oid;
        struct strbuf buf = STRBUF_INIT;
        const char *ident;
        time_t now;
        int size, len;
        struct cache_entry *ce;
        unsigned mode;
        struct strbuf msg = STRBUF_INIT;

        read_cache();
        time(&now);
        commit = alloc_commit_node();
        commit->object.parsed = 1;
        commit->date = now;
        parent_tail = &commit->parents;

        if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_oid.hash, NULL))
                die("no such ref: HEAD");

        parent_tail = append_parent(parent_tail, &head_oid);
        append_merge_parents(parent_tail);
        verify_working_tree_path(commit, path);

        origin = make_origin(commit, path);

        ident = fmt_ident("Not Committed Yet", "not.committed.yet", NULL, 0);
        strbuf_addstr(&msg, "tree 0000000000000000000000000000000000000000\n");
        for (parent = commit->parents; parent; parent = parent->next)
                strbuf_addf(&msg, "parent %s\n",
                            oid_to_hex(&parent->item->object.oid));
        strbuf_addf(&msg,
                    "author %s\n"
                    "committer %s\n\n"
                    "Version of %s from %s\n",
                    ident, ident, path,
                    (!contents_from ? path :
                     (!strcmp(contents_from, "-") ? "standard input" : contents_from)));
        set_commit_buffer_from_strbuf(commit, &msg);

        if (!contents_from || strcmp("-", contents_from)) {
                struct stat st;
                const char *read_from;
                char *buf_ptr;
                unsigned long buf_len;

                if (contents_from) {
                        if (stat(contents_from, &st) < 0)
                                die_errno("Cannot stat '%s'", contents_from);
                        read_from = contents_from;
                }
                else {
                        if (lstat(path, &st) < 0)
                                die_errno("Cannot lstat '%s'", path);
                        read_from = path;
                }
                mode = canon_mode(st.st_mode);

                switch (st.st_mode & S_IFMT) {
                case S_IFREG:
                        if (DIFF_OPT_TST(opt, ALLOW_TEXTCONV) &&
                            textconv_object(read_from, mode, &null_oid, 0, &buf_ptr, &buf_len))
                                strbuf_attach(&buf, buf_ptr, buf_len, buf_len + 1);
                        else if (strbuf_read_file(&buf, read_from, st.st_size) != st.st_size)
                                die_errno("cannot open or read '%s'", read_from);
                        break;
                case S_IFLNK:
                        if (strbuf_readlink(&buf, read_from, st.st_size) < 0)
                                die_errno("cannot readlink '%s'", read_from);
                        break;
                default:
                        die("unsupported file type %s", read_from);
                }
        }
        else {
                /* Reading from stdin */
                mode = 0;
                if (strbuf_read(&buf, 0, 0) < 0)
                        die_errno("failed to read from stdin");
        }
        convert_to_git(path, buf.buf, buf.len, &buf, 0);
        origin->file.ptr = buf.buf;
        origin->file.size = buf.len;
        pretend_sha1_file(buf.buf, buf.len, OBJ_BLOB, origin->blob_oid.hash);

        /*
         * Read the current index, replace the path entry with
         * origin->blob_sha1 without mucking with its mode or type
         * bits; we are not going to write this index out -- we just
         * want to run "diff-index --cached".
         */
        discard_cache();
        read_cache();

        len = strlen(path);
        if (!mode) {
                int pos = cache_name_pos(path, len);
                if (0 <= pos)
                        mode = active_cache[pos]->ce_mode;
                else
                        /* Let's not bother reading from HEAD tree */
                        mode = S_IFREG | 0644;
        }
        size = cache_entry_size(len);
        ce = xcalloc(1, size);
        oidcpy(&ce->oid, &origin->blob_oid);
        memcpy(ce->name, path, len);
        ce->ce_flags = create_ce_flags(0);
        ce->ce_namelen = len;
        ce->ce_mode = create_ce_mode(mode);
        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);

        cache_tree_invalidate_path(&the_index, path);

        return commit;
}

static struct commit *find_single_final(struct rev_info *revs,
                                        const char **name_p)
{
        int i;
        struct commit *found = NULL;
        const char *name = NULL;

        for (i = 0; i < revs->pending.nr; i++) {
                struct object *obj = revs->pending.objects[i].item;
                if (obj->flags & UNINTERESTING)
                        continue;
                obj = deref_tag(obj, NULL, 0);
                if (obj->type != OBJ_COMMIT)
                        die("Non commit %s?", revs->pending.objects[i].name);
                if (found)
                        die("More than one commit to dig from %s and %s?",
                            revs->pending.objects[i].name, name);
                found = (struct commit *)obj;
                name = revs->pending.objects[i].name;
        }
        if (name_p)
                *name_p = name;
        return found;
}

static char *prepare_final(struct scoreboard *sb)
{
        const char *name;
        sb->final = find_single_final(sb->revs, &name);
        return xstrdup_or_null(name);
}

static const char *dwim_reverse_initial(struct scoreboard *sb)
{
        /*
         * DWIM "git blame --reverse ONE -- PATH" as
         * "git blame --reverse ONE..HEAD -- PATH" but only do so
         * when it makes sense.
         */
        struct object *obj;
        struct commit *head_commit;
        unsigned char head_sha1[20];

        if (sb->revs->pending.nr != 1)
                return NULL;

        /* Is that sole rev a committish? */
        obj = sb->revs->pending.objects[0].item;
        obj = deref_tag(obj, NULL, 0);
        if (obj->type != OBJ_COMMIT)
                return NULL;

        /* Do we have HEAD? */
        if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_sha1, NULL))
                return NULL;
        head_commit = lookup_commit_reference_gently(head_sha1, 1);
        if (!head_commit)
                return NULL;

        /* Turn "ONE" into "ONE..HEAD" then */
        obj->flags |= UNINTERESTING;
        add_pending_object(sb->revs, &head_commit->object, "HEAD");

        sb->final = (struct commit *)obj;
        return sb->revs->pending.objects[0].name;
}

static char *prepare_initial(struct scoreboard *sb)
{
        int i;
        const char *final_commit_name = NULL;
        struct rev_info *revs = sb->revs;

        /*
         * There must be one and only one negative commit, and it must be
         * the boundary.
         */
        for (i = 0; i < revs->pending.nr; i++) {
                struct object *obj = revs->pending.objects[i].item;
                if (!(obj->flags & UNINTERESTING))
                        continue;
                obj = deref_tag(obj, NULL, 0);
                if (obj->type != OBJ_COMMIT)
                        die("Non commit %s?", revs->pending.objects[i].name);
                if (sb->final)
                        die("More than one commit to dig up from, %s and %s?",
                            revs->pending.objects[i].name,
                            final_commit_name);
                sb->final = (struct commit *) obj;
                final_commit_name = revs->pending.objects[i].name;
        }

        if (!final_commit_name)
                final_commit_name = dwim_reverse_initial(sb);
        if (!final_commit_name)
                die("No commit to dig up from?");
        return xstrdup(final_commit_name);
}

static int blame_copy_callback(const struct option *option, const char *arg, int unset)
{
        int *opt = option->value;

        /*
         * -C enables copy from removed files;
         * -C -C enables copy from existing files, but only
         *       when blaming a new file;
         * -C -C -C enables copy from existing files for
         *          everybody
         */
        if (*opt & PICKAXE_BLAME_COPY_HARDER)
                *opt |= PICKAXE_BLAME_COPY_HARDEST;
        if (*opt & PICKAXE_BLAME_COPY)
                *opt |= PICKAXE_BLAME_COPY_HARDER;
        *opt |= PICKAXE_BLAME_COPY | PICKAXE_BLAME_MOVE;

        if (arg)
                blame_copy_score = parse_score(arg);
        return 0;
}

static int blame_move_callback(const struct option *option, const char *arg, int unset)
{
        int *opt = option->value;

        *opt |= PICKAXE_BLAME_MOVE;

        if (arg)
                blame_move_score = parse_score(arg);
        return 0;
}

int cmd_blame(int argc, const char **argv, const char *prefix)
{
        struct rev_info revs;
        const char *path;
        struct scoreboard sb;
        struct origin *o;
        struct blame_entry *ent = NULL;
        long dashdash_pos, lno;
        char *final_commit_name = NULL;
        enum object_type type;
        struct commit *final_commit = NULL;

        struct string_list range_list = STRING_LIST_INIT_NODUP;
        int output_option = 0, opt = 0;
        int show_stats = 0;
        const char *revs_file = NULL;
        const char *contents_from = NULL;
        const struct option options[] = {
                OPT_BOOL(0, "incremental", &incremental, N_("Show blame entries as we find them, incrementally")),
                OPT_BOOL('b', NULL, &blank_boundary, N_("Show blank SHA-1 for boundary commits (Default: off)")),
                OPT_BOOL(0, "root", &show_root, N_("Do not treat root commits as boundaries (Default: off)")),
                OPT_BOOL(0, "show-stats", &show_stats, N_("Show work cost statistics")),
                OPT_BOOL(0, "progress", &show_progress, N_("Force progress reporting")),
                OPT_BIT(0, "score-debug", &output_option, N_("Show output score for blame entries"), OUTPUT_SHOW_SCORE),
                OPT_BIT('f', "show-name", &output_option, N_("Show original filename (Default: auto)"), OUTPUT_SHOW_NAME),
                OPT_BIT('n', "show-number", &output_option, N_("Show original linenumber (Default: off)"), OUTPUT_SHOW_NUMBER),
                OPT_BIT('p', "porcelain", &output_option, N_("Show in a format designed for machine consumption"), OUTPUT_PORCELAIN),
                OPT_BIT(0, "line-porcelain", &output_option, N_("Show porcelain format with per-line commit information"), OUTPUT_PORCELAIN|OUTPUT_LINE_PORCELAIN),
                OPT_BIT('c', NULL, &output_option, N_("Use the same output mode as git-annotate (Default: off)"), OUTPUT_ANNOTATE_COMPAT),
                OPT_BIT('t', NULL, &output_option, N_("Show raw timestamp (Default: off)"), OUTPUT_RAW_TIMESTAMP),
                OPT_BIT('l', NULL, &output_option, N_("Show long commit SHA1 (Default: off)"), OUTPUT_LONG_OBJECT_NAME),
                OPT_BIT('s', NULL, &output_option, N_("Suppress author name and timestamp (Default: off)"), OUTPUT_NO_AUTHOR),
                OPT_BIT('e', "show-email", &output_option, N_("Show author email instead of name (Default: off)"), OUTPUT_SHOW_EMAIL),
                OPT_BIT('w', NULL, &xdl_opts, N_("Ignore whitespace differences"), XDF_IGNORE_WHITESPACE),

                /*
                 * The following two options are parsed by parse_revision_opt()
                 * and are only included here to get included in the "-h"
                 * output:
                 */
                { OPTION_LOWLEVEL_CALLBACK, 0, "indent-heuristic", NULL, NULL, N_("Use an experimental heuristic to improve diffs"), PARSE_OPT_NOARG, parse_opt_unknown_cb },

                OPT_BIT(0, "minimal", &xdl_opts, N_("Spend extra cycles to find better match"), XDF_NEED_MINIMAL),
                OPT_STRING('S', NULL, &revs_file, N_("file"), N_("Use revisions from <file> instead of calling git-rev-list")),
                OPT_STRING(0, "contents", &contents_from, N_("file"), N_("Use <file>'s contents as the final image")),
                { OPTION_CALLBACK, 'C', NULL, &opt, N_("score"), N_("Find line copies within and across files"), PARSE_OPT_OPTARG, blame_copy_callback },
                { OPTION_CALLBACK, 'M', NULL, &opt, N_("score"), N_("Find line movements within and across files"), PARSE_OPT_OPTARG, blame_move_callback },
                OPT_STRING_LIST('L', NULL, &range_list, N_("n,m"), N_("Process only line range n,m, counting from 1")),
                OPT__ABBREV(&abbrev),
                OPT_END()
        };

        struct parse_opt_ctx_t ctx;
        int cmd_is_annotate = !strcmp(argv[0], "annotate");
        struct range_set ranges;
        unsigned int range_i;
        long anchor;

        git_config(git_blame_config, &output_option);
        init_revisions(&revs, NULL);
        revs.date_mode = blame_date_mode;
        DIFF_OPT_SET(&revs.diffopt, ALLOW_TEXTCONV);
        DIFF_OPT_SET(&revs.diffopt, FOLLOW_RENAMES);

        save_commit_buffer = 0;
        dashdash_pos = 0;
        show_progress = -1;

        parse_options_start(&ctx, argc, argv, prefix, options,
                            PARSE_OPT_KEEP_DASHDASH | PARSE_OPT_KEEP_ARGV0);
        for (;;) {
                switch (parse_options_step(&ctx, options, blame_opt_usage)) {
                case PARSE_OPT_HELP:
                        exit(129);
                case PARSE_OPT_DONE:
                        if (ctx.argv[0])
                                dashdash_pos = ctx.cpidx;
                        goto parse_done;
                }

                if (!strcmp(ctx.argv[0], "--reverse")) {
                        ctx.argv[0] = "--children";
                        reverse = 1;
                }
                parse_revision_opt(&revs, &ctx, options, blame_opt_usage);
        }
parse_done:
        no_whole_file_rename = !DIFF_OPT_TST(&revs.diffopt, FOLLOW_RENAMES);
        xdl_opts |= revs.diffopt.xdl_opts & XDF_INDENT_HEURISTIC;
        DIFF_OPT_CLR(&revs.diffopt, FOLLOW_RENAMES);
        argc = parse_options_end(&ctx);

        if (incremental || (output_option & OUTPUT_PORCELAIN)) {
                if (show_progress > 0)
                        die(_("--progress can't be used with --incremental or porcelain formats"));
                show_progress = 0;
        } else if (show_progress < 0)
                show_progress = isatty(2);

        if (0 < abbrev && abbrev < GIT_SHA1_HEXSZ)
                /* one more abbrev length is needed for the boundary commit */
                abbrev++;
        else if (!abbrev)
                abbrev = GIT_SHA1_HEXSZ;

        if (revs_file && read_ancestry(revs_file))
                die_errno("reading graft file '%s' failed", revs_file);

        if (cmd_is_annotate) {
                output_option |= OUTPUT_ANNOTATE_COMPAT;
                blame_date_mode.type = DATE_ISO8601;
        } else {
                blame_date_mode = revs.date_mode;
        }

        /* The maximum width used to show the dates */
        switch (blame_date_mode.type) {
        case DATE_RFC2822:
                blame_date_width = sizeof("Thu, 19 Oct 2006 16:00:04 -0700");
                break;
        case DATE_ISO8601_STRICT:
                blame_date_width = sizeof("2006-10-19T16:00:04-07:00");
                break;
        case DATE_ISO8601:
                blame_date_width = sizeof("2006-10-19 16:00:04 -0700");
                break;
        case DATE_RAW:
                blame_date_width = sizeof("1161298804 -0700");
                break;
        case DATE_UNIX:
                blame_date_width = sizeof("1161298804");
                break;
        case DATE_SHORT:
                blame_date_width = sizeof("2006-10-19");
                break;
        case DATE_RELATIVE:
                /* TRANSLATORS: This string is used to tell us the maximum
                   display width for a relative timestamp in "git blame"
                   output.  For C locale, "4 years, 11 months ago", which
                   takes 22 places, is the longest among various forms of
                   relative timestamps, but your language may need more or
                   fewer display columns. */
                blame_date_width = utf8_strwidth(_("4 years, 11 months ago")) + 1; /* add the null */
                break;
        case DATE_NORMAL:
                blame_date_width = sizeof("Thu Oct 19 16:00:04 2006 -0700");
                break;
        case DATE_STRFTIME:
                blame_date_width = strlen(show_date(0, 0, &blame_date_mode)) + 1; /* add the null */
                break;
        }
        blame_date_width -= 1; /* strip the null */

        if (DIFF_OPT_TST(&revs.diffopt, FIND_COPIES_HARDER))
                opt |= (PICKAXE_BLAME_COPY | PICKAXE_BLAME_MOVE |
                        PICKAXE_BLAME_COPY_HARDER);

        if (!blame_move_score)
                blame_move_score = BLAME_DEFAULT_MOVE_SCORE;
        if (!blame_copy_score)
                blame_copy_score = BLAME_DEFAULT_COPY_SCORE;

        /*
         * We have collected options unknown to us in argv[1..unk]
         * which are to be passed to revision machinery if we are
         * going to do the "bottom" processing.
         *
         * The remaining are:
         *
         * (1) if dashdash_pos != 0, it is either
         *     "blame [revisions] -- <path>" or
         *     "blame -- <path> <rev>"
         *
         * (2) otherwise, it is one of the two:
         *     "blame [revisions] <path>"
         *     "blame <path> <rev>"
         *
         * Note that we must strip out <path> from the arguments: we do not
         * want the path pruning but we may want "bottom" processing.
         */
        if (dashdash_pos) {
                switch (argc - dashdash_pos - 1) {
                case 2: /* (1b) */
                        if (argc != 4)
                                usage_with_options(blame_opt_usage, options);
                        /* reorder for the new way: <rev> -- <path> */
                        argv[1] = argv[3];
                        argv[3] = argv[2];
                        argv[2] = "--";
                        /* FALLTHROUGH */
                case 1: /* (1a) */
                        path = add_prefix(prefix, argv[--argc]);
                        argv[argc] = NULL;
                        break;
                default:
                        usage_with_options(blame_opt_usage, options);
                }
        } else {
                if (argc < 2)
                        usage_with_options(blame_opt_usage, options);
                path = add_prefix(prefix, argv[argc - 1]);
                if (argc == 3 && !file_exists(path)) { /* (2b) */
                        path = add_prefix(prefix, argv[1]);
                        argv[1] = argv[2];
                }
                argv[argc - 1] = "--";

                setup_work_tree();
                if (!file_exists(path))
                        die_errno("cannot stat path '%s'", path);
        }

        revs.disable_stdin = 1;
        setup_revisions(argc, argv, &revs, NULL);
        memset(&sb, 0, sizeof(sb));

        sb.revs = &revs;
        if (!reverse) {
                final_commit_name = prepare_final(&sb);
                sb.commits.compare = compare_commits_by_commit_date;
        }
        else if (contents_from)
                die(_("--contents and --reverse do not blend well."));
        else {
                final_commit_name = prepare_initial(&sb);
                sb.commits.compare = compare_commits_by_reverse_commit_date;
                if (revs.first_parent_only)
                        revs.children.name = NULL;
        }

        if (!sb.final) {
                /*
                 * "--not A B -- path" without anything positive;
                 * do not default to HEAD, but use the working tree
                 * or "--contents".
                 */
                setup_work_tree();
                sb.final = fake_working_tree_commit(&sb.revs->diffopt,
                                                    path, contents_from);
                add_pending_object(&revs, &(sb.final->object), ":");
        }
        else if (contents_from)
                die(_("cannot use --contents with final commit object name"));

        if (reverse && revs.first_parent_only) {
                final_commit = find_single_final(sb.revs, NULL);
                if (!final_commit)
                        die(_("--reverse and --first-parent together require specified latest commit"));
        }

        /*
         * If we have bottom, this will mark the ancestors of the
         * bottom commits we would reach while traversing as
         * uninteresting.
         */
        if (prepare_revision_walk(&revs))
                die(_("revision walk setup failed"));

        if (reverse && revs.first_parent_only) {
                struct commit *c = final_commit;

                sb.revs->children.name = "children";
                while (c->parents &&
                       oidcmp(&c->object.oid, &sb.final->object.oid)) {
                        struct commit_list *l = xcalloc(1, sizeof(*l));

                        l->item = c;
                        if (add_decoration(&sb.revs->children,
                                           &c->parents->item->object, l))
                                die("BUG: not unique item in first-parent chain");
                        c = c->parents->item;
                }

                if (oidcmp(&c->object.oid, &sb.final->object.oid))
                        die(_("--reverse --first-parent together require range along first-parent chain"));
        }

        if (is_null_oid(&sb.final->object.oid)) {
                o = sb.final->util;
                sb.final_buf = xmemdupz(o->file.ptr, o->file.size);
                sb.final_buf_size = o->file.size;
        }
        else {
                o = get_origin(&sb, sb.final, path);
                if (fill_blob_sha1_and_mode(o))
                        die(_("no such path %s in %s"), path, final_commit_name);

                if (DIFF_OPT_TST(&sb.revs->diffopt, ALLOW_TEXTCONV) &&
                    textconv_object(path, o->mode, &o->blob_oid, 1, (char **) &sb.final_buf,
                                    &sb.final_buf_size))
                        ;
                else
                        sb.final_buf = read_sha1_file(o->blob_oid.hash, &type,
                                                      &sb.final_buf_size);

                if (!sb.final_buf)
                        die(_("cannot read blob %s for path %s"),
                            oid_to_hex(&o->blob_oid),
                            path);
        }
        num_read_blob++;
        lno = prepare_lines(&sb);

        if (lno && !range_list.nr)
                string_list_append(&range_list, "1");

        anchor = 1;
        range_set_init(&ranges, range_list.nr);
        for (range_i = 0; range_i < range_list.nr; ++range_i) {
                long bottom, top;
                if (parse_range_arg(range_list.items[range_i].string,
                                    nth_line_cb, &sb, lno, anchor,
                                    &bottom, &top, sb.path))
                        usage(blame_usage);
                if (lno < top || ((lno || bottom) && lno < bottom))
                        die(Q_("file %s has only %lu line",
                               "file %s has only %lu lines",
                               lno), path, lno);
                if (bottom < 1)
                        bottom = 1;
                if (top < 1)
                        top = lno;
                bottom--;
                range_set_append_unsafe(&ranges, bottom, top);
                anchor = top + 1;
        }
        sort_and_merge_range_set(&ranges);

        for (range_i = ranges.nr; range_i > 0; --range_i) {
                const struct range *r = &ranges.ranges[range_i - 1];
                long bottom = r->start;
                long top = r->end;
                struct blame_entry *next = ent;
                ent = xcalloc(1, sizeof(*ent));
                ent->lno = bottom;
                ent->num_lines = top - bottom;
                ent->suspect = o;
                ent->s_lno = bottom;
                ent->next = next;
                origin_incref(o);
        }

        o->suspects = ent;
        prio_queue_put(&sb.commits, o->commit);

        origin_decref(o);

        range_set_release(&ranges);
        string_list_clear(&range_list, 0);

        sb.ent = NULL;
        sb.path = path;

        read_mailmap(&mailmap, NULL);

        assign_blame(&sb, opt);

        if (!incremental)
                setup_pager();

        free(final_commit_name);

        if (incremental)
                return 0;

        sb.ent = blame_sort(sb.ent, compare_blame_final);

        coalesce(&sb);

        if (!(output_option & OUTPUT_PORCELAIN))
                find_alignment(&sb, &output_option);

        output(&sb, output_option);
        free((void *)sb.final_buf);
        for (ent = sb.ent; ent; ) {
                struct blame_entry *e = ent->next;
                free(ent);
                ent = e;
        }

        if (show_stats) {
                printf("num read blob: %d\n", num_read_blob);
                printf("num get patch: %d\n", num_get_patch);
                printf("num commits: %d\n", num_commits);
        }
        return 0;
}