fast-export: allow seeding the anonymized mapping

[thirdparty/git.git] / builtin / fast-export.c

/*
 * "git fast-export" builtin command
 *
 * Copyright (C) 2007 Johannes E. Schindelin
 */
#include "builtin.h"
#include "cache.h"
#include "config.h"
#include "refs.h"
#include "refspec.h"
#include "object-store.h"
#include "commit.h"
#include "object.h"
#include "tag.h"
#include "diff.h"
#include "diffcore.h"
#include "log-tree.h"
#include "revision.h"
#include "decorate.h"
#include "string-list.h"
#include "utf8.h"
#include "parse-options.h"
#include "quote.h"
#include "remote.h"
#include "blob.h"
#include "commit-slab.h"

static const char *fast_export_usage[] = {
        N_("git fast-export [rev-list-opts]"),
        NULL
};

static int progress;
static enum { SIGNED_TAG_ABORT, VERBATIM, WARN, WARN_STRIP, STRIP } signed_tag_mode = SIGNED_TAG_ABORT;
static enum { TAG_FILTERING_ABORT, DROP, REWRITE } tag_of_filtered_mode = TAG_FILTERING_ABORT;
static enum { REENCODE_ABORT, REENCODE_YES, REENCODE_NO } reencode_mode = REENCODE_ABORT;
static int fake_missing_tagger;
static int use_done_feature;
static int no_data;
static int full_tree;
static int reference_excluded_commits;
static int show_original_ids;
static int mark_tags;
static struct string_list extra_refs = STRING_LIST_INIT_NODUP;
static struct string_list tag_refs = STRING_LIST_INIT_NODUP;
static struct refspec refspecs = REFSPEC_INIT_FETCH;
static int anonymize;
static struct hashmap anonymized_seeds;
static struct revision_sources revision_sources;

static int parse_opt_signed_tag_mode(const struct option *opt,
                                     const char *arg, int unset)
{
        if (unset || !strcmp(arg, "abort"))
                signed_tag_mode = SIGNED_TAG_ABORT;
        else if (!strcmp(arg, "verbatim") || !strcmp(arg, "ignore"))
                signed_tag_mode = VERBATIM;
        else if (!strcmp(arg, "warn"))
                signed_tag_mode = WARN;
        else if (!strcmp(arg, "warn-strip"))
                signed_tag_mode = WARN_STRIP;
        else if (!strcmp(arg, "strip"))
                signed_tag_mode = STRIP;
        else
                return error("Unknown signed-tags mode: %s", arg);
        return 0;
}

static int parse_opt_tag_of_filtered_mode(const struct option *opt,
                                          const char *arg, int unset)
{
        if (unset || !strcmp(arg, "abort"))
                tag_of_filtered_mode = TAG_FILTERING_ABORT;
        else if (!strcmp(arg, "drop"))
                tag_of_filtered_mode = DROP;
        else if (!strcmp(arg, "rewrite"))
                tag_of_filtered_mode = REWRITE;
        else
                return error("Unknown tag-of-filtered mode: %s", arg);
        return 0;
}

static int parse_opt_reencode_mode(const struct option *opt,
                                   const char *arg, int unset)
{
        if (unset) {
                reencode_mode = REENCODE_ABORT;
                return 0;
        }

        switch (git_parse_maybe_bool(arg)) {
        case 0:
                reencode_mode = REENCODE_NO;
                break;
        case 1:
                reencode_mode = REENCODE_YES;
                break;
        default:
                if (!strcasecmp(arg, "abort"))
                        reencode_mode = REENCODE_ABORT;
                else
                        return error("Unknown reencoding mode: %s", arg);
        }

        return 0;
}

static struct decoration idnums;
static uint32_t last_idnum;

static int has_unshown_parent(struct commit *commit)
{
        struct commit_list *parent;

        for (parent = commit->parents; parent; parent = parent->next)
                if (!(parent->item->object.flags & SHOWN) &&
                    !(parent->item->object.flags & UNINTERESTING))
                        return 1;
        return 0;
}

struct anonymized_entry {
        struct hashmap_entry hash;
        const char *anon;
        const char orig[FLEX_ARRAY];
};

struct anonymized_entry_key {
        struct hashmap_entry hash;
        const char *orig;
        size_t orig_len;
};

static int anonymized_entry_cmp(const void *unused_cmp_data,
                                const struct hashmap_entry *eptr,
                                const struct hashmap_entry *entry_or_key,
                                const void *keydata)
{
        const struct anonymized_entry *a, *b;

        a = container_of(eptr, const struct anonymized_entry, hash);
        if (keydata) {
                const struct anonymized_entry_key *key = keydata;
                int equal = !strncmp(a->orig, key->orig, key->orig_len) &&
                            !a->orig[key->orig_len];
                return !equal;
        }

        b = container_of(entry_or_key, const struct anonymized_entry, hash);
        return strcmp(a->orig, b->orig);
}

/*
 * Basically keep a cache of X->Y so that we can repeatedly replace
 * the same anonymized string with another. The actual generation
 * is farmed out to the generate function.
 */
static const char *anonymize_str(struct hashmap *map,
                                 char *(*generate)(void *),
                                 const char *orig, size_t len,
                                 void *data)
{
        struct anonymized_entry_key key;
        struct anonymized_entry *ret;

        if (!map->cmpfn)
                hashmap_init(map, anonymized_entry_cmp, NULL, 0);

        hashmap_entry_init(&key.hash, memhash(orig, len));
        key.orig = orig;
        key.orig_len = len;

        /* First check if it's a token the user configured manually... */
        if (anonymized_seeds.cmpfn)
                ret = hashmap_get_entry(&anonymized_seeds, &key, hash, &key);
        else
                ret = NULL;

        /* ...otherwise check if we've already seen it in this context... */
        if (!ret)
                ret = hashmap_get_entry(map, &key, hash, &key);

        /* ...and finally generate a new mapping if necessary */
        if (!ret) {
                FLEX_ALLOC_MEM(ret, orig, orig, len);
                hashmap_entry_init(&ret->hash, key.hash.hash);
                ret->anon = generate(data);
                hashmap_put(map, &ret->hash);
        }

        return ret->anon;
}

/*
 * We anonymize each component of a path individually,
 * so that paths a/b and a/c will share a common root.
 * The paths are cached via anonymize_mem so that repeated
 * lookups for "a" will yield the same value.
 */
static void anonymize_path(struct strbuf *out, const char *path,
                           struct hashmap *map,
                           char *(*generate)(void *))
{
        while (*path) {
                const char *end_of_component = strchrnul(path, '/');
                size_t len = end_of_component - path;
                const char *c = anonymize_str(map, generate, path, len, NULL);
                strbuf_addstr(out, c);
                path = end_of_component;
                if (*path)
                        strbuf_addch(out, *path++);
        }
}

static inline void *mark_to_ptr(uint32_t mark)
{
        return (void *)(uintptr_t)mark;
}

static inline uint32_t ptr_to_mark(void * mark)
{
        return (uint32_t)(uintptr_t)mark;
}

static inline void mark_object(struct object *object, uint32_t mark)
{
        add_decoration(&idnums, object, mark_to_ptr(mark));
}

static inline void mark_next_object(struct object *object)
{
        mark_object(object, ++last_idnum);
}

static int get_object_mark(struct object *object)
{
        void *decoration = lookup_decoration(&idnums, object);
        if (!decoration)
                return 0;
        return ptr_to_mark(decoration);
}

static struct commit *rewrite_commit(struct commit *p)
{
        for (;;) {
                if (p->parents && p->parents->next)
                        break;
                if (p->object.flags & UNINTERESTING)
                        break;
                if (!(p->object.flags & TREESAME))
                        break;
                if (!p->parents)
                        return NULL;
                p = p->parents->item;
        }
        return p;
}

static void show_progress(void)
{
        static int counter = 0;
        if (!progress)
                return;
        if ((++counter % progress) == 0)
                printf("progress %d objects\n", counter);
}

/*
 * Ideally we would want some transformation of the blob data here
 * that is unreversible, but would still be the same size and have
 * the same data relationship to other blobs (so that we get the same
 * delta and packing behavior as the original). But the first and last
 * requirements there are probably mutually exclusive, so let's take
 * the easy way out for now, and just generate arbitrary content.
 *
 * There's no need to cache this result with anonymize_mem, since
 * we already handle blob content caching with marks.
 */
static char *anonymize_blob(unsigned long *size)
{
        static int counter;
        struct strbuf out = STRBUF_INIT;
        strbuf_addf(&out, "anonymous blob %d", counter++);
        *size = out.len;
        return strbuf_detach(&out, NULL);
}

static void export_blob(const struct object_id *oid)
{
        unsigned long size;
        enum object_type type;
        char *buf;
        struct object *object;
        int eaten;

        if (no_data)
                return;

        if (is_null_oid(oid))
                return;

        object = lookup_object(the_repository, oid);
        if (object && object->flags & SHOWN)
                return;

        if (anonymize) {
                buf = anonymize_blob(&size);
                object = (struct object *)lookup_blob(the_repository, oid);
                eaten = 0;
        } else {
                buf = read_object_file(oid, &type, &size);
                if (!buf)
                        die("could not read blob %s", oid_to_hex(oid));
                if (check_object_signature(the_repository, oid, buf, size,
                                           type_name(type)) < 0)
                        die("oid mismatch in blob %s", oid_to_hex(oid));
                object = parse_object_buffer(the_repository, oid, type,
                                             size, buf, &eaten);
        }

        if (!object)
                die("Could not read blob %s", oid_to_hex(oid));

        mark_next_object(object);

        printf("blob\nmark :%"PRIu32"\n", last_idnum);
        if (show_original_ids)
                printf("original-oid %s\n", oid_to_hex(oid));
        printf("data %"PRIuMAX"\n", (uintmax_t)size);
        if (size && fwrite(buf, size, 1, stdout) != 1)
                die_errno("could not write blob '%s'", oid_to_hex(oid));
        printf("\n");

        show_progress();

        object->flags |= SHOWN;
        if (!eaten)
                free(buf);
}

static int depth_first(const void *a_, const void *b_)
{
        const struct diff_filepair *a = *((const struct diff_filepair **)a_);
        const struct diff_filepair *b = *((const struct diff_filepair **)b_);
        const char *name_a, *name_b;
        int len_a, len_b, len;
        int cmp;

        name_a = a->one ? a->one->path : a->two->path;
        name_b = b->one ? b->one->path : b->two->path;

        len_a = strlen(name_a);
        len_b = strlen(name_b);
        len = (len_a < len_b) ? len_a : len_b;

        /* strcmp will sort 'd' before 'd/e', we want 'd/e' before 'd' */
        cmp = memcmp(name_a, name_b, len);
        if (cmp)
                return cmp;
        cmp = len_b - len_a;
        if (cmp)
                return cmp;
        /*
         * Move 'R'ename entries last so that all references of the file
         * appear in the output before it is renamed (e.g., when a file
         * was copied and renamed in the same commit).
         */
        return (a->status == 'R') - (b->status == 'R');
}

static void print_path_1(const char *path)
{
        int need_quote = quote_c_style(path, NULL, NULL, 0);
        if (need_quote)
                quote_c_style(path, NULL, stdout, 0);
        else if (strchr(path, ' '))
                printf("\"%s\"", path);
        else
                printf("%s", path);
}

static char *anonymize_path_component(void *data)
{
        static int counter;
        struct strbuf out = STRBUF_INIT;
        strbuf_addf(&out, "path%d", counter++);
        return strbuf_detach(&out, NULL);
}

static void print_path(const char *path)
{
        if (!anonymize)
                print_path_1(path);
        else {
                static struct hashmap paths;
                static struct strbuf anon = STRBUF_INIT;

                anonymize_path(&anon, path, &paths, anonymize_path_component);
                print_path_1(anon.buf);
                strbuf_reset(&anon);
        }
}

static char *generate_fake_oid(void *data)
{
        static uint32_t counter = 1; /* avoid null oid */
        const unsigned hashsz = the_hash_algo->rawsz;
        struct object_id oid;
        char *hex = xmallocz(GIT_MAX_HEXSZ);

        oidclr(&oid);
        put_be32(oid.hash + hashsz - 4, counter++);
        return oid_to_hex_r(hex, &oid);
}

static const char *anonymize_oid(const char *oid_hex)
{
        static struct hashmap objs;
        size_t len = strlen(oid_hex);
        return anonymize_str(&objs, generate_fake_oid, oid_hex, len, NULL);
}

static void show_filemodify(struct diff_queue_struct *q,
                            struct diff_options *options, void *data)
{
        int i;
        struct string_list *changed = data;

        /*
         * Handle files below a directory first, in case they are all deleted
         * and the directory changes to a file or symlink.
         */
        QSORT(q->queue, q->nr, depth_first);

        for (i = 0; i < q->nr; i++) {
                struct diff_filespec *ospec = q->queue[i]->one;
                struct diff_filespec *spec = q->queue[i]->two;

                switch (q->queue[i]->status) {
                case DIFF_STATUS_DELETED:
                        printf("D ");
                        print_path(spec->path);
                        string_list_insert(changed, spec->path);
                        putchar('\n');
                        break;

                case DIFF_STATUS_COPIED:
                case DIFF_STATUS_RENAMED:
                        /*
                         * If a change in the file corresponding to ospec->path
                         * has been observed, we cannot trust its contents
                         * because the diff is calculated based on the prior
                         * contents, not the current contents.  So, declare a
                         * copy or rename only if there was no change observed.
                         */
                        if (!string_list_has_string(changed, ospec->path)) {
                                printf("%c ", q->queue[i]->status);
                                print_path(ospec->path);
                                putchar(' ');
                                print_path(spec->path);
                                string_list_insert(changed, spec->path);
                                putchar('\n');

                                if (oideq(&ospec->oid, &spec->oid) &&
                                    ospec->mode == spec->mode)
                                        break;
                        }
                        /* fallthrough */

                case DIFF_STATUS_TYPE_CHANGED:
                case DIFF_STATUS_MODIFIED:
                case DIFF_STATUS_ADDED:
                        /*
                         * Links refer to objects in another repositories;
                         * output the SHA-1 verbatim.
                         */
                        if (no_data || S_ISGITLINK(spec->mode))
                                printf("M %06o %s ", spec->mode,
                                       anonymize ?
                                       anonymize_oid(oid_to_hex(&spec->oid)) :
                                       oid_to_hex(&spec->oid));
                        else {
                                struct object *object = lookup_object(the_repository,
                                                                      &spec->oid);
                                printf("M %06o :%d ", spec->mode,
                                       get_object_mark(object));
                        }
                        print_path(spec->path);
                        string_list_insert(changed, spec->path);
                        putchar('\n');
                        break;

                default:
                        die("Unexpected comparison status '%c' for %s, %s",
                                q->queue[i]->status,
                                ospec->path ? ospec->path : "none",
                                spec->path ? spec->path : "none");
                }
        }
}

static const char *find_encoding(const char *begin, const char *end)
{
        const char *needle = "\nencoding ";
        char *bol, *eol;

        bol = memmem(begin, end ? end - begin : strlen(begin),
                     needle, strlen(needle));
        if (!bol)
                return NULL;
        bol += strlen(needle);
        eol = strchrnul(bol, '\n');
        *eol = '\0';
        return bol;
}

static char *anonymize_ref_component(void *data)
{
        static int counter;
        struct strbuf out = STRBUF_INIT;
        strbuf_addf(&out, "ref%d", counter++);
        return strbuf_detach(&out, NULL);
}

static const char *anonymize_refname(const char *refname)
{
        /*
         * If any of these prefixes is found, we will leave it intact
         * so that tags remain tags and so forth.
         */
        static const char *prefixes[] = {
                "refs/heads/",
                "refs/tags/",
                "refs/remotes/",
                "refs/"
        };
        static struct hashmap refs;
        static struct strbuf anon = STRBUF_INIT;
        int i;

        /*
         * We also leave "master" as a special case, since it does not reveal
         * anything interesting.
         */
        if (!strcmp(refname, "refs/heads/master"))
                return refname;

        strbuf_reset(&anon);
        for (i = 0; i < ARRAY_SIZE(prefixes); i++) {
                if (skip_prefix(refname, prefixes[i], &refname)) {
                        strbuf_addstr(&anon, prefixes[i]);
                        break;
                }
        }

        anonymize_path(&anon, refname, &refs, anonymize_ref_component);
        return anon.buf;
}

/*
 * We do not even bother to cache commit messages, as they are unlikely
 * to be repeated verbatim, and it is not that interesting when they are.
 */
static char *anonymize_commit_message(const char *old)
{
        static int counter;
        return xstrfmt("subject %d\n\nbody\n", counter++);
}

static char *anonymize_ident(void *data)
{
        static int counter;
        struct strbuf out = STRBUF_INIT;
        strbuf_addf(&out, "User %d <user%d@example.com>", counter, counter);
        counter++;
        return strbuf_detach(&out, NULL);
}

/*
 * Our strategy here is to anonymize the names and email addresses,
 * but keep timestamps intact, as they influence things like traversal
 * order (and by themselves should not be too revealing).
 */
static void anonymize_ident_line(const char **beg, const char **end)
{
        static struct hashmap idents;
        static struct strbuf buffers[] = { STRBUF_INIT, STRBUF_INIT };
        static unsigned which_buffer;

        struct strbuf *out;
        struct ident_split split;
        const char *end_of_header;

        out = &buffers[which_buffer++];
        which_buffer %= ARRAY_SIZE(buffers);
        strbuf_reset(out);

        /* skip "committer", "author", "tagger", etc */
        end_of_header = strchr(*beg, ' ');
        if (!end_of_header)
                BUG("malformed line fed to anonymize_ident_line: %.*s",
                    (int)(*end - *beg), *beg);
        end_of_header++;
        strbuf_add(out, *beg, end_of_header - *beg);

        if (!split_ident_line(&split, end_of_header, *end - end_of_header) &&
            split.date_begin) {
                const char *ident;
                size_t len;

                len = split.mail_end - split.name_begin;
                ident = anonymize_str(&idents, anonymize_ident,
                                      split.name_begin, len, NULL);
                strbuf_addstr(out, ident);
                strbuf_addch(out, ' ');
                strbuf_add(out, split.date_begin, split.tz_end - split.date_begin);
        } else {
                strbuf_addstr(out, "Malformed Ident <malformed@example.com> 0 -0000");
        }

        *beg = out->buf;
        *end = out->buf + out->len;
}

static void handle_commit(struct commit *commit, struct rev_info *rev,
                          struct string_list *paths_of_changed_objects)
{
        int saved_output_format = rev->diffopt.output_format;
        const char *commit_buffer;
        const char *author, *author_end, *committer, *committer_end;
        const char *encoding, *message;
        char *reencoded = NULL;
        struct commit_list *p;
        const char *refname;
        int i;

        rev->diffopt.output_format = DIFF_FORMAT_CALLBACK;

        parse_commit_or_die(commit);
        commit_buffer = get_commit_buffer(commit, NULL);
        author = strstr(commit_buffer, "\nauthor ");
        if (!author)
                die("could not find author in commit %s",
                    oid_to_hex(&commit->object.oid));
        author++;
        author_end = strchrnul(author, '\n');
        committer = strstr(author_end, "\ncommitter ");
        if (!committer)
                die("could not find committer in commit %s",
                    oid_to_hex(&commit->object.oid));
        committer++;
        committer_end = strchrnul(committer, '\n');
        message = strstr(committer_end, "\n\n");
        encoding = find_encoding(committer_end, message);
        if (message)
                message += 2;

        if (commit->parents &&
            (get_object_mark(&commit->parents->item->object) != 0 ||
             reference_excluded_commits) &&
            !full_tree) {
                parse_commit_or_die(commit->parents->item);
                diff_tree_oid(get_commit_tree_oid(commit->parents->item),
                              get_commit_tree_oid(commit), "", &rev->diffopt);
        }
        else
                diff_root_tree_oid(get_commit_tree_oid(commit),
                                   "", &rev->diffopt);

        /* Export the referenced blobs, and remember the marks. */
        for (i = 0; i < diff_queued_diff.nr; i++)
                if (!S_ISGITLINK(diff_queued_diff.queue[i]->two->mode))
                        export_blob(&diff_queued_diff.queue[i]->two->oid);

        refname = *revision_sources_at(&revision_sources, commit);
        /*
         * FIXME: string_list_remove() below for each ref is overall
         * O(N^2).  Compared to a history walk and diffing trees, this is
         * just lost in the noise in practice.  However, theoretically a
         * repo may have enough refs for this to become slow.
         */
        string_list_remove(&extra_refs, refname, 0);
        if (anonymize) {
                refname = anonymize_refname(refname);
                anonymize_ident_line(&committer, &committer_end);
                anonymize_ident_line(&author, &author_end);
        }

        mark_next_object(&commit->object);
        if (anonymize) {
                reencoded = anonymize_commit_message(message);
        } else if (encoding) {
                switch(reencode_mode) {
                case REENCODE_YES:
                        reencoded = reencode_string(message, "UTF-8", encoding);
                        break;
                case REENCODE_NO:
                        break;
                case REENCODE_ABORT:
                        die("Encountered commit-specific encoding %s in commit "
                            "%s; use --reencode=[yes|no] to handle it",
                            encoding, oid_to_hex(&commit->object.oid));
                }
        }
        if (!commit->parents)
                printf("reset %s\n", refname);
        printf("commit %s\nmark :%"PRIu32"\n", refname, last_idnum);
        if (show_original_ids)
                printf("original-oid %s\n", oid_to_hex(&commit->object.oid));
        printf("%.*s\n%.*s\n",
               (int)(author_end - author), author,
               (int)(committer_end - committer), committer);
        if (!reencoded && encoding)
                printf("encoding %s\n", encoding);
        printf("data %u\n%s",
               (unsigned)(reencoded
                          ? strlen(reencoded) : message
                          ? strlen(message) : 0),
               reencoded ? reencoded : message ? message : "");
        free(reencoded);
        unuse_commit_buffer(commit, commit_buffer);

        for (i = 0, p = commit->parents; p; p = p->next) {
                struct object *obj = &p->item->object;
                int mark = get_object_mark(obj);

                if (!mark && !reference_excluded_commits)
                        continue;
                if (i == 0)
                        printf("from ");
                else
                        printf("merge ");
                if (mark)
                        printf(":%d\n", mark);
                else
                        printf("%s\n",
                               anonymize ?
                               anonymize_oid(oid_to_hex(&obj->oid)) :
                               oid_to_hex(&obj->oid));
                i++;
        }

        if (full_tree)
                printf("deleteall\n");
        log_tree_diff_flush(rev);
        string_list_clear(paths_of_changed_objects, 0);
        rev->diffopt.output_format = saved_output_format;

        printf("\n");

        show_progress();
}

static char *anonymize_tag(void *data)
{
        static int counter;
        struct strbuf out = STRBUF_INIT;
        strbuf_addf(&out, "tag message %d", counter++);
        return strbuf_detach(&out, NULL);
}

static void handle_tail(struct object_array *commits, struct rev_info *revs,
                        struct string_list *paths_of_changed_objects)
{
        struct commit *commit;
        while (commits->nr) {
                commit = (struct commit *)object_array_pop(commits);
                if (has_unshown_parent(commit)) {
                        /* Queue again, to be handled later */
                        add_object_array(&commit->object, NULL, commits);
                        return;
                }
                handle_commit(commit, revs, paths_of_changed_objects);
        }
}

static void handle_tag(const char *name, struct tag *tag)
{
        unsigned long size;
        enum object_type type;
        char *buf;
        const char *tagger, *tagger_end, *message;
        size_t message_size = 0;
        struct object *tagged;
        int tagged_mark;
        struct commit *p;

        /* Trees have no identifier in fast-export output, thus we have no way
         * to output tags of trees, tags of tags of trees, etc.  Simply omit
         * such tags.
         */
        tagged = tag->tagged;
        while (tagged->type == OBJ_TAG) {
                tagged = ((struct tag *)tagged)->tagged;
        }
        if (tagged->type == OBJ_TREE) {
                warning("Omitting tag %s,\nsince tags of trees (or tags of tags of trees, etc.) are not supported.",
                        oid_to_hex(&tag->object.oid));
                return;
        }

        buf = read_object_file(&tag->object.oid, &type, &size);
        if (!buf)
                die("could not read tag %s", oid_to_hex(&tag->object.oid));
        message = memmem(buf, size, "\n\n", 2);
        if (message) {
                message += 2;
                message_size = strlen(message);
        }
        tagger = memmem(buf, message ? message - buf : size, "\ntagger ", 8);
        if (!tagger) {
                if (fake_missing_tagger)
                        tagger = "tagger Unspecified Tagger "
                                "<unspecified-tagger> 0 +0000";
                else
                        tagger = "";
                tagger_end = tagger + strlen(tagger);
        } else {
                tagger++;
                tagger_end = strchrnul(tagger, '\n');
                if (anonymize)
                        anonymize_ident_line(&tagger, &tagger_end);
        }

        if (anonymize) {
                name = anonymize_refname(name);
                if (message) {
                        static struct hashmap tags;
                        message = anonymize_str(&tags, anonymize_tag,
                                                message, message_size, NULL);
                }
        }

        /* handle signed tags */
        if (message) {
                const char *signature = strstr(message,
                                               "\n-----BEGIN PGP SIGNATURE-----\n");
                if (signature)
                        switch(signed_tag_mode) {
                        case SIGNED_TAG_ABORT:
                                die("encountered signed tag %s; use "
                                    "--signed-tags=<mode> to handle it",
                                    oid_to_hex(&tag->object.oid));
                        case WARN:
                                warning("exporting signed tag %s",
                                        oid_to_hex(&tag->object.oid));
                                /* fallthru */
                        case VERBATIM:
                                break;
                        case WARN_STRIP:
                                warning("stripping signature from tag %s",
                                        oid_to_hex(&tag->object.oid));
                                /* fallthru */
                        case STRIP:
                                message_size = signature + 1 - message;
                                break;
                        }
        }

        /* handle tag->tagged having been filtered out due to paths specified */
        tagged = tag->tagged;
        tagged_mark = get_object_mark(tagged);
        if (!tagged_mark) {
                switch(tag_of_filtered_mode) {
                case TAG_FILTERING_ABORT:
                        die("tag %s tags unexported object; use "
                            "--tag-of-filtered-object=<mode> to handle it",
                            oid_to_hex(&tag->object.oid));
                case DROP:
                        /* Ignore this tag altogether */
                        free(buf);
                        return;
                case REWRITE:
                        if (tagged->type == OBJ_TAG && !mark_tags) {
                                die(_("Error: Cannot export nested tags unless --mark-tags is specified."));
                        } else if (tagged->type == OBJ_COMMIT) {
                                p = rewrite_commit((struct commit *)tagged);
                                if (!p) {
                                        printf("reset %s\nfrom %s\n\n",
                                               name, oid_to_hex(&null_oid));
                                        free(buf);
                                        return;
                                }
                                tagged_mark = get_object_mark(&p->object);
                        } else {
                                /* tagged->type is either OBJ_BLOB or OBJ_TAG */
                                tagged_mark = get_object_mark(tagged);
                        }
                }
        }

        if (tagged->type == OBJ_TAG) {
                printf("reset %s\nfrom %s\n\n",
                       name, oid_to_hex(&null_oid));
        }
        skip_prefix(name, "refs/tags/", &name);
        printf("tag %s\n", name);
        if (mark_tags) {
                mark_next_object(&tag->object);
                printf("mark :%"PRIu32"\n", last_idnum);
        }
        if (tagged_mark)
                printf("from :%d\n", tagged_mark);
        else
                printf("from %s\n", oid_to_hex(&tagged->oid));

        if (show_original_ids)
                printf("original-oid %s\n", oid_to_hex(&tag->object.oid));
        printf("%.*s%sdata %d\n%.*s\n",
               (int)(tagger_end - tagger), tagger,
               tagger == tagger_end ? "" : "\n",
               (int)message_size, (int)message_size, message ? message : "");
        free(buf);
}

static struct commit *get_commit(struct rev_cmdline_entry *e, char *full_name)
{
        switch (e->item->type) {
        case OBJ_COMMIT:
                return (struct commit *)e->item;
        case OBJ_TAG: {
                struct tag *tag = (struct tag *)e->item;

                /* handle nested tags */
                while (tag && tag->object.type == OBJ_TAG) {
                        parse_object(the_repository, &tag->object.oid);
                        string_list_append(&tag_refs, full_name)->util = tag;
                        tag = (struct tag *)tag->tagged;
                }
                if (!tag)
                        die("Tag %s points nowhere?", e->name);
                return (struct commit *)tag;
                break;
        }
        default:
                return NULL;
        }
}

static void get_tags_and_duplicates(struct rev_cmdline_info *info)
{
        int i;

        for (i = 0; i < info->nr; i++) {
                struct rev_cmdline_entry *e = info->rev + i;
                struct object_id oid;
                struct commit *commit;
                char *full_name;

                if (e->flags & UNINTERESTING)
                        continue;

                if (dwim_ref(e->name, strlen(e->name), &oid, &full_name) != 1)
                        continue;

                if (refspecs.nr) {
                        char *private;
                        private = apply_refspecs(&refspecs, full_name);
                        if (private) {
                                free(full_name);
                                full_name = private;
                        }
                }

                commit = get_commit(e, full_name);
                if (!commit) {
                        warning("%s: Unexpected object of type %s, skipping.",
                                e->name,
                                type_name(e->item->type));
                        continue;
                }

                switch(commit->object.type) {
                case OBJ_COMMIT:
                        break;
                case OBJ_BLOB:
                        export_blob(&commit->object.oid);
                        continue;
                default: /* OBJ_TAG (nested tags) is already handled */
                        warning("Tag points to object of unexpected type %s, skipping.",
                                type_name(commit->object.type));
                        continue;
                }

                /*
                 * Make sure this ref gets properly updated eventually, whether
                 * through a commit or manually at the end.
                 */
                if (e->item->type != OBJ_TAG)
                        string_list_append(&extra_refs, full_name)->util = commit;

                if (!*revision_sources_at(&revision_sources, commit))
                        *revision_sources_at(&revision_sources, commit) = full_name;
        }

        string_list_sort(&extra_refs);
        string_list_remove_duplicates(&extra_refs, 0);
}

static void handle_tags_and_duplicates(struct string_list *extras)
{
        struct commit *commit;
        int i;

        for (i = extras->nr - 1; i >= 0; i--) {
                const char *name = extras->items[i].string;
                struct object *object = extras->items[i].util;
                int mark;

                switch (object->type) {
                case OBJ_TAG:
                        handle_tag(name, (struct tag *)object);
                        break;
                case OBJ_COMMIT:
                        if (anonymize)
                                name = anonymize_refname(name);
                        /* create refs pointing to already seen commits */
                        commit = rewrite_commit((struct commit *)object);
                        if (!commit) {
                                /*
                                 * Neither this object nor any of its
                                 * ancestors touch any relevant paths, so
                                 * it has been filtered to nothing.  Delete
                                 * it.
                                 */
                                printf("reset %s\nfrom %s\n\n",
                                       name, oid_to_hex(&null_oid));
                                continue;
                        }

                        mark = get_object_mark(&commit->object);
                        if (!mark) {
                                /*
                                 * Getting here means we have a commit which
                                 * was excluded by a negative refspec (e.g.
                                 * fast-export ^master master).  If we are
                                 * referencing excluded commits, set the ref
                                 * to the exact commit.  Otherwise, the user
                                 * wants the branch exported but every commit
                                 * in its history to be deleted, which basically
                                 * just means deletion of the ref.
                                 */
                                if (!reference_excluded_commits) {
                                        /* delete the ref */
                                        printf("reset %s\nfrom %s\n\n",
                                               name, oid_to_hex(&null_oid));
                                        continue;
                                }
                                /* set ref to commit using oid, not mark */
                                printf("reset %s\nfrom %s\n\n", name,
                                       oid_to_hex(&commit->object.oid));
                                continue;
                        }

                        printf("reset %s\nfrom :%d\n\n", name, mark
                               );
                        show_progress();
                        break;
                }
        }
}

static void export_marks(char *file)
{
        unsigned int i;
        uint32_t mark;
        struct decoration_entry *deco = idnums.entries;
        FILE *f;
        int e = 0;

        f = fopen_for_writing(file);
        if (!f)
                die_errno("Unable to open marks file %s for writing.", file);

        for (i = 0; i < idnums.size; i++) {
                if (deco->base && deco->base->type == 1) {
                        mark = ptr_to_mark(deco->decoration);
                        if (fprintf(f, ":%"PRIu32" %s\n", mark,
                                oid_to_hex(&deco->base->oid)) < 0) {
                            e = 1;
                            break;
                        }
                }
                deco++;
        }

        e |= ferror(f);
        e |= fclose(f);
        if (e)
                error("Unable to write marks file %s.", file);
}

static void import_marks(char *input_file, int check_exists)
{
        char line[512];
        FILE *f;
        struct stat sb;

        if (check_exists && stat(input_file, &sb))
                return;

        f = xfopen(input_file, "r");
        while (fgets(line, sizeof(line), f)) {
                uint32_t mark;
                char *line_end, *mark_end;
                struct object_id oid;
                struct object *object;
                struct commit *commit;
                enum object_type type;

                line_end = strchr(line, '\n');
                if (line[0] != ':' || !line_end)
                        die("corrupt mark line: %s", line);
                *line_end = '\0';

                mark = strtoumax(line + 1, &mark_end, 10);
                if (!mark || mark_end == line + 1
                        || *mark_end != ' ' || get_oid_hex(mark_end + 1, &oid))
                        die("corrupt mark line: %s", line);

                if (last_idnum < mark)
                        last_idnum = mark;

                type = oid_object_info(the_repository, &oid, NULL);
                if (type < 0)
                        die("object not found: %s", oid_to_hex(&oid));

                if (type != OBJ_COMMIT)
                        /* only commits */
                        continue;

                commit = lookup_commit(the_repository, &oid);
                if (!commit)
                        die("not a commit? can't happen: %s", oid_to_hex(&oid));

                object = &commit->object;

                if (object->flags & SHOWN)
                        error("Object %s already has a mark", oid_to_hex(&oid));

                mark_object(object, mark);

                object->flags |= SHOWN;
        }
        fclose(f);
}

static void handle_deletes(void)
{
        int i;
        for (i = 0; i < refspecs.nr; i++) {
                struct refspec_item *refspec = &refspecs.items[i];
                if (*refspec->src)
                        continue;

                printf("reset %s\nfrom %s\n\n",
                                refspec->dst, oid_to_hex(&null_oid));
        }
}

static char *anonymize_seed(void *data)
{
        return xstrdup(data);
}

static int parse_opt_anonymize_map(const struct option *opt,
                                   const char *arg, int unset)
{
        struct hashmap *map = opt->value;
        const char *delim, *value;
        size_t keylen;

        BUG_ON_OPT_NEG(unset);

        delim = strchr(arg, ':');
        if (delim) {
                keylen = delim - arg;
                value = delim + 1;
        } else {
                keylen = strlen(arg);
                value = arg;
        }

        if (!keylen || !*value)
                return error(_("--anonymize-map token cannot be empty"));

        anonymize_str(map, anonymize_seed, arg, keylen, (void *)value);

        return 0;
}

int cmd_fast_export(int argc, const char **argv, const char *prefix)
{
        struct rev_info revs;
        struct object_array commits = OBJECT_ARRAY_INIT;
        struct commit *commit;
        char *export_filename = NULL,
             *import_filename = NULL,
             *import_filename_if_exists = NULL;
        uint32_t lastimportid;
        struct string_list refspecs_list = STRING_LIST_INIT_NODUP;
        struct string_list paths_of_changed_objects = STRING_LIST_INIT_DUP;
        struct option options[] = {
                OPT_INTEGER(0, "progress", &progress,
                            N_("show progress after <n> objects")),
                OPT_CALLBACK(0, "signed-tags", &signed_tag_mode, N_("mode"),
                             N_("select handling of signed tags"),
                             parse_opt_signed_tag_mode),
                OPT_CALLBACK(0, "tag-of-filtered-object", &tag_of_filtered_mode, N_("mode"),
                             N_("select handling of tags that tag filtered objects"),
                             parse_opt_tag_of_filtered_mode),
                OPT_CALLBACK(0, "reencode", &reencode_mode, N_("mode"),
                             N_("select handling of commit messages in an alternate encoding"),
                             parse_opt_reencode_mode),
                OPT_STRING(0, "export-marks", &export_filename, N_("file"),
                             N_("Dump marks to this file")),
                OPT_STRING(0, "import-marks", &import_filename, N_("file"),
                             N_("Import marks from this file")),
                OPT_STRING(0, "import-marks-if-exists",
                             &import_filename_if_exists,
                             N_("file"),
                             N_("Import marks from this file if it exists")),
                OPT_BOOL(0, "fake-missing-tagger", &fake_missing_tagger,
                         N_("Fake a tagger when tags lack one")),
                OPT_BOOL(0, "full-tree", &full_tree,
                         N_("Output full tree for each commit")),
                OPT_BOOL(0, "use-done-feature", &use_done_feature,
                             N_("Use the done feature to terminate the stream")),
                OPT_BOOL(0, "no-data", &no_data, N_("Skip output of blob data")),
                OPT_STRING_LIST(0, "refspec", &refspecs_list, N_("refspec"),
                             N_("Apply refspec to exported refs")),
                OPT_BOOL(0, "anonymize", &anonymize, N_("anonymize output")),
                OPT_CALLBACK_F(0, "anonymize-map", &anonymized_seeds, N_("from:to"),
                               N_("convert <from> to <to> in anonymized output"),
                               PARSE_OPT_NONEG, parse_opt_anonymize_map),
                OPT_BOOL(0, "reference-excluded-parents",
                         &reference_excluded_commits, N_("Reference parents which are not in fast-export stream by object id")),
                OPT_BOOL(0, "show-original-ids", &show_original_ids,
                            N_("Show original object ids of blobs/commits")),
                OPT_BOOL(0, "mark-tags", &mark_tags,
                            N_("Label tags with mark ids")),

                OPT_END()
        };

        if (argc == 1)
                usage_with_options (fast_export_usage, options);

        /* we handle encodings */
        git_config(git_default_config, NULL);

        repo_init_revisions(the_repository, &revs, prefix);
        init_revision_sources(&revision_sources);
        revs.topo_order = 1;
        revs.sources = &revision_sources;
        revs.rewrite_parents = 1;
        argc = parse_options(argc, argv, prefix, options, fast_export_usage,
                        PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN);
        argc = setup_revisions(argc, argv, &revs, NULL);
        if (argc > 1)
                usage_with_options (fast_export_usage, options);

        if (anonymized_seeds.cmpfn && !anonymize)
                die(_("--anonymize-map without --anonymize does not make sense"));

        if (refspecs_list.nr) {
                int i;

                for (i = 0; i < refspecs_list.nr; i++)
                        refspec_append(&refspecs, refspecs_list.items[i].string);

                string_list_clear(&refspecs_list, 1);
        }

        if (use_done_feature)
                printf("feature done\n");

        if (import_filename && import_filename_if_exists)
                die(_("Cannot pass both --import-marks and --import-marks-if-exists"));
        if (import_filename)
                import_marks(import_filename, 0);
        else if (import_filename_if_exists)
                import_marks(import_filename_if_exists, 1);
        lastimportid = last_idnum;

        if (import_filename && revs.prune_data.nr)
                full_tree = 1;

        get_tags_and_duplicates(&revs.cmdline);

        if (prepare_revision_walk(&revs))
                die("revision walk setup failed");
        revs.diffopt.format_callback = show_filemodify;
        revs.diffopt.format_callback_data = &paths_of_changed_objects;
        revs.diffopt.flags.recursive = 1;
        while ((commit = get_revision(&revs))) {
                if (has_unshown_parent(commit)) {
                        add_object_array(&commit->object, NULL, &commits);
                }
                else {
                        handle_commit(commit, &revs, &paths_of_changed_objects);
                        handle_tail(&commits, &revs, &paths_of_changed_objects);
                }
        }

        handle_tags_and_duplicates(&extra_refs);
        handle_tags_and_duplicates(&tag_refs);
        handle_deletes();

        if (export_filename && lastimportid != last_idnum)
                export_marks(export_filename);

        if (use_done_feature)
                printf("done\n");

        refspec_clear(&refspecs);

        return 0;
}