fetch: support fetching from a shallow repository

[thirdparty/git.git] / shallow.c

#include "cache.h"
#include "commit.h"
#include "tag.h"
#include "pkt-line.h"
#include "remote.h"
#include "refs.h"
#include "sha1-array.h"
#include "diff.h"
#include "revision.h"
#include "commit-slab.h"

static int is_shallow = -1;
static struct stat shallow_stat;
static char *alternate_shallow_file;

void set_alternate_shallow_file(const char *path)
{
	if (is_shallow != -1)
		die("BUG: is_repository_shallow must not be called before set_alternate_shallow_file");
	free(alternate_shallow_file);
	alternate_shallow_file = path ? xstrdup(path) : NULL;
}

int register_shallow(const unsigned char *sha1)
{
	struct commit_graft *graft =
		xmalloc(sizeof(struct commit_graft));
	struct commit *commit = lookup_commit(sha1);

	hashcpy(graft->sha1, sha1);
	graft->nr_parent = -1;
	if (commit && commit->object.parsed)
		commit->parents = NULL;
	return register_commit_graft(graft, 0);
}

int is_repository_shallow(void)
{
	FILE *fp;
	char buf[1024];
	const char *path = alternate_shallow_file;

	if (is_shallow >= 0)
		return is_shallow;

	if (!path)
		path = git_path("shallow");
	/*
	 * fetch-pack sets '--shallow-file ""' as an indicator that no
	 * shallow file should be used. We could just open it and it
	 * will likely fail. But let's do an explicit check instead.
	 */
	if (!*path ||
	    stat(path, &shallow_stat) ||
	    (fp = fopen(path, "r")) == NULL) {
		is_shallow = 0;
		return is_shallow;
	}
	is_shallow = 1;

	while (fgets(buf, sizeof(buf), fp)) {
		unsigned char sha1[20];
		if (get_sha1_hex(buf, sha1))
			die("bad shallow line: %s", buf);
		register_shallow(sha1);
	}
	fclose(fp);
	return is_shallow;
}

struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
		int shallow_flag, int not_shallow_flag)
{
	int i = 0, cur_depth = 0;
	struct commit_list *result = NULL;
	struct object_array stack = OBJECT_ARRAY_INIT;
	struct commit *commit = NULL;

	while (commit || i < heads->nr || stack.nr) {
		struct commit_list *p;
		if (!commit) {
			if (i < heads->nr) {
				commit = (struct commit *)
					deref_tag(heads->objects[i++].item, NULL, 0);
				if (!commit || commit->object.type != OBJ_COMMIT) {
					commit = NULL;
					continue;
				}
				if (!commit->util)
					commit->util = xmalloc(sizeof(int));
				*(int *)commit->util = 0;
				cur_depth = 0;
			} else {
				commit = (struct commit *)
					stack.objects[--stack.nr].item;
				cur_depth = *(int *)commit->util;
			}
		}
		if (parse_commit(commit))
			die("invalid commit");
		cur_depth++;
		if (cur_depth >= depth) {
			commit_list_insert(commit, &result);
			commit->object.flags |= shallow_flag;
			commit = NULL;
			continue;
		}
		commit->object.flags |= not_shallow_flag;
		for (p = commit->parents, commit = NULL; p; p = p->next) {
			if (!p->item->util) {
				int *pointer = xmalloc(sizeof(int));
				p->item->util = pointer;
				*pointer =  cur_depth;
			} else {
				int *pointer = p->item->util;
				if (cur_depth >= *pointer)
					continue;
				*pointer = cur_depth;
			}
			if (p->next)
				add_object_array(&p->item->object,
						NULL, &stack);
			else {
				commit = p->item;
				cur_depth = *(int *)commit->util;
			}
		}
	}

	return result;
}

void check_shallow_file_for_update(void)
{
	struct stat st;

	if (!is_shallow)
		return;
	else if (is_shallow == -1)
		die("BUG: shallow must be initialized by now");

	if (stat(git_path("shallow"), &st))
		die("shallow file was removed during fetch");
	else if (st.st_mtime != shallow_stat.st_mtime
#ifdef USE_NSEC
		 || ST_MTIME_NSEC(st) != ST_MTIME_NSEC(shallow_stat)
#endif
		   )
		die("shallow file was changed during fetch");
}

struct write_shallow_data {
	struct strbuf *out;
	int use_pack_protocol;
	int count;
};

static int write_one_shallow(const struct commit_graft *graft, void *cb_data)
{
	struct write_shallow_data *data = cb_data;
	const char *hex = sha1_to_hex(graft->sha1);
	if (graft->nr_parent != -1)
		return 0;
	data->count++;
	if (data->use_pack_protocol)
		packet_buf_write(data->out, "shallow %s", hex);
	else {
		strbuf_addstr(data->out, hex);
		strbuf_addch(data->out, '\n');
	}
	return 0;
}

int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
			  const struct sha1_array *extra)
{
	struct write_shallow_data data;
	int i;
	data.out = out;
	data.use_pack_protocol = use_pack_protocol;
	data.count = 0;
	for_each_commit_graft(write_one_shallow, &data);
	if (!extra)
		return data.count;
	for (i = 0; i < extra->nr; i++) {
		strbuf_addstr(out, sha1_to_hex(extra->sha1[i]));
		strbuf_addch(out, '\n');
		data.count++;
	}
	return data.count;
}

char *setup_temporary_shallow(const struct sha1_array *extra)
{
	struct strbuf sb = STRBUF_INIT;
	int fd;

	if (write_shallow_commits(&sb, 0, extra)) {
		struct strbuf path = STRBUF_INIT;
		strbuf_addstr(&path, git_path("shallow_XXXXXX"));
		fd = xmkstemp(path.buf);
		if (write_in_full(fd, sb.buf, sb.len) != sb.len)
			die_errno("failed to write to %s",
				  path.buf);
		close(fd);
		strbuf_release(&sb);
		return strbuf_detach(&path, NULL);
	}
	/*
	 * is_repository_shallow() sees empty string as "no shallow
	 * file".
	 */
	return xstrdup("");
}

void setup_alternate_shallow(struct lock_file *shallow_lock,
			     const char **alternate_shallow_file,
			     const struct sha1_array *extra)
{
	struct strbuf sb = STRBUF_INIT;
	int fd;

	check_shallow_file_for_update();
	fd = hold_lock_file_for_update(shallow_lock, git_path("shallow"),
				       LOCK_DIE_ON_ERROR);
	if (write_shallow_commits(&sb, 0, extra)) {
		if (write_in_full(fd, sb.buf, sb.len) != sb.len)
			die_errno("failed to write to %s",
				  shallow_lock->filename);
		*alternate_shallow_file = shallow_lock->filename;
	} else
		/*
		 * is_repository_shallow() sees empty string as "no
		 * shallow file".
		 */
		*alternate_shallow_file = "";
	strbuf_release(&sb);
}

static int advertise_shallow_grafts_cb(const struct commit_graft *graft, void *cb)
{
	int fd = *(int *)cb;
	if (graft->nr_parent == -1)
		packet_write(fd, "shallow %s\n", sha1_to_hex(graft->sha1));
	return 0;
}

void advertise_shallow_grafts(int fd)
{
	if (!is_repository_shallow())
		return;
	for_each_commit_graft(advertise_shallow_grafts_cb, &fd);
}

#define TRACE_KEY "GIT_TRACE_SHALLOW"

/*
 * Step 1, split sender shallow commits into "ours" and "theirs"
 * Step 2, clean "ours" based on .git/shallow
 */
void prepare_shallow_info(struct shallow_info *info, struct sha1_array *sa)
{
	int i;
	trace_printf_key(TRACE_KEY, "shallow: prepare_shallow_info\n");
	memset(info, 0, sizeof(*info));
	info->shallow = sa;
	if (!sa)
		return;
	info->ours = xmalloc(sizeof(*info->ours) * sa->nr);
	info->theirs = xmalloc(sizeof(*info->theirs) * sa->nr);
	for (i = 0; i < sa->nr; i++) {
		if (has_sha1_file(sa->sha1[i])) {
			struct commit_graft *graft;
			graft = lookup_commit_graft(sa->sha1[i]);
			if (graft && graft->nr_parent < 0)
				continue;
			info->ours[info->nr_ours++] = i;
		} else
			info->theirs[info->nr_theirs++] = i;
	}
}

void clear_shallow_info(struct shallow_info *info)
{
	free(info->ours);
	free(info->theirs);
}

/* Step 4, remove non-existent ones in "theirs" after getting the pack */

void remove_nonexistent_theirs_shallow(struct shallow_info *info)
{
	unsigned char (*sha1)[20] = info->shallow->sha1;
	int i, dst;
	trace_printf_key(TRACE_KEY, "shallow: remove_nonexistent_theirs_shallow\n");
	for (i = dst = 0; i < info->nr_theirs; i++) {
		if (i != dst)
			info->theirs[dst] = info->theirs[i];
		if (has_sha1_file(sha1[info->theirs[i]]))
			dst++;
	}
	info->nr_theirs = dst;
}

/* Step 5, remove non-existent ones in "ours" in the pack */
void remove_nonexistent_ours_in_pack(struct shallow_info *info,
				     struct packed_git *p)
{
	unsigned char (*sha1)[20] = info->shallow->sha1;
	int i, dst;
	trace_printf_key(TRACE_KEY, "shallow: remove_nonexistent_ours_in_pack\n");
	for (i = dst = 0; i < info->nr_ours; i++) {
		if (i != dst)
			info->ours[dst] = info->ours[i];
		if (find_pack_entry_one(sha1[info->ours[i]], p))
			dst++;
	}
	info->nr_ours = dst;
}

define_commit_slab(ref_bitmap, uint32_t *);

struct paint_info {
	struct ref_bitmap ref_bitmap;
	unsigned nr_bits;
	char **slab;
	char *free, *end;
	unsigned slab_count;
};

static uint32_t *paint_alloc(struct paint_info *info)
{
	unsigned nr = (info->nr_bits + 31) / 32;
	unsigned size = nr * sizeof(uint32_t);
	void *p;
	if (!info->slab_count || info->free + size > info->end) {
		info->slab_count++;
		info->slab = xrealloc(info->slab,
				      info->slab_count * sizeof(*info->slab));
		info->free = xmalloc(COMMIT_SLAB_SIZE);
		info->slab[info->slab_count - 1] = info->free;
		info->end = info->free + COMMIT_SLAB_SIZE;
	}
	p = info->free;
	info->free += size;
	return p;
}

/*
 * Given a commit SHA-1, walk down to parents until either SEEN,
 * UNINTERESTING or BOTTOM is hit. Set the id-th bit in ref_bitmap for
 * all walked commits.
 */
static void paint_down(struct paint_info *info, const unsigned char *sha1,
		       int id)
{
	unsigned int i, nr;
	struct commit_list *head = NULL;
	int bitmap_nr = (info->nr_bits + 31) / 32;
	int bitmap_size = bitmap_nr * sizeof(uint32_t);
	uint32_t *tmp = xmalloc(bitmap_size); /* to be freed before return */
	uint32_t *bitmap = paint_alloc(info);
	struct commit *c = lookup_commit_reference_gently(sha1, 1);
	if (!c)
		return;
	memset(bitmap, 0, bitmap_size);
	bitmap[id / 32] |= (1 << (id % 32));
	commit_list_insert(c, &head);
	while (head) {
		struct commit_list *p;
		struct commit *c = head->item;
		uint32_t **refs = ref_bitmap_at(&info->ref_bitmap, c);

		p = head;
		head = head->next;
		free(p);

		/* XXX check "UNINTERESTING" from pack bitmaps if available */
		if (c->object.flags & (SEEN | UNINTERESTING))
			continue;
		else
			c->object.flags |= SEEN;

		if (*refs == NULL)
			*refs = bitmap;
		else {
			memcpy(tmp, *refs, bitmap_size);
			for (i = 0; i < bitmap_nr; i++)
				tmp[i] |= bitmap[i];
			if (memcmp(tmp, *refs, bitmap_size)) {
				*refs = paint_alloc(info);
				memcpy(*refs, tmp, bitmap_size);
			}
		}

		if (c->object.flags & BOTTOM)
			continue;

		if (parse_commit(c))
			die("unable to parse commit %s",
			    sha1_to_hex(c->object.sha1));

		for (p = c->parents; p; p = p->next) {
			uint32_t **p_refs = ref_bitmap_at(&info->ref_bitmap,
							  p->item);
			if (p->item->object.flags & SEEN)
				continue;
			if (*p_refs == NULL || *p_refs == *refs)
				*p_refs = *refs;
			commit_list_insert(p->item, &head);
		}
	}

	nr = get_max_object_index();
	for (i = 0; i < nr; i++) {
		struct object *o = get_indexed_object(i);
		if (o && o->type == OBJ_COMMIT)
			o->flags &= ~SEEN;
	}

	free(tmp);
}

static int mark_uninteresting(const char *refname,
			      const unsigned char *sha1,
			      int flags, void *cb_data)
{
	struct commit *commit = lookup_commit_reference_gently(sha1, 1);
	if (!commit)
		return 0;
	commit->object.flags |= UNINTERESTING;
	mark_parents_uninteresting(commit);
	return 0;
}

static void post_assign_shallow(struct shallow_info *info,
				struct ref_bitmap *ref_bitmap,
				int *ref_status);
/*
 * Step 6(+7), associate shallow commits with new refs
 *
 * info->ref must be initialized before calling this function.
 *
 * If used is not NULL, it's an array of info->shallow->nr
 * bitmaps. The n-th bit set in the m-th bitmap if ref[n] needs the
 * m-th shallow commit from info->shallow.
 *
 * If used is NULL, "ours" and "theirs" are updated. And if ref_status
 * is not NULL it's an array of ref->nr ints. ref_status[i] is true if
 * the ref needs some shallow commits from either info->ours or
 * info->theirs.
 */
void assign_shallow_commits_to_refs(struct shallow_info *info,
				    uint32_t **used, int *ref_status)
{
	unsigned char (*sha1)[20] = info->shallow->sha1;
	struct sha1_array *ref = info->ref;
	unsigned int i, nr;
	int *shallow, nr_shallow = 0;
	struct paint_info pi;

	trace_printf_key(TRACE_KEY, "shallow: assign_shallow_commits_to_refs\n");
	shallow = xmalloc(sizeof(*shallow) * (info->nr_ours + info->nr_theirs));
	for (i = 0; i < info->nr_ours; i++)
		shallow[nr_shallow++] = info->ours[i];
	for (i = 0; i < info->nr_theirs; i++)
		shallow[nr_shallow++] = info->theirs[i];

	/*
	 * Prepare the commit graph to track what refs can reach what
	 * (new) shallow commits.
	 */
	nr = get_max_object_index();
	for (i = 0; i < nr; i++) {
		struct object *o = get_indexed_object(i);
		if (!o || o->type != OBJ_COMMIT)
			continue;

		o->flags &= ~(UNINTERESTING | BOTTOM | SEEN);
	}

	memset(&pi, 0, sizeof(pi));
	init_ref_bitmap(&pi.ref_bitmap);
	pi.nr_bits = ref->nr;

	/*
	 * "--not --all" to cut short the traversal if new refs
	 * connect to old refs. If not (e.g. force ref updates) it'll
	 * have to go down to the current shallow commits.
	 */
	head_ref(mark_uninteresting, NULL);
	for_each_ref(mark_uninteresting, NULL);

	/* Mark potential bottoms so we won't go out of bound */
	for (i = 0; i < nr_shallow; i++) {
		struct commit *c = lookup_commit(sha1[shallow[i]]);
		c->object.flags |= BOTTOM;
	}

	for (i = 0; i < ref->nr; i++)
		paint_down(&pi, ref->sha1[i], i);

	if (used) {
		int bitmap_size = ((pi.nr_bits + 31) / 32) * sizeof(uint32_t);
		memset(used, 0, sizeof(*used) * info->shallow->nr);
		for (i = 0; i < nr_shallow; i++) {
			const struct commit *c = lookup_commit(sha1[shallow[i]]);
			uint32_t **map = ref_bitmap_at(&pi.ref_bitmap, c);
			if (*map)
				used[shallow[i]] = xmemdupz(*map, bitmap_size);
		}
		/*
		 * unreachable shallow commits are not removed from
		 * "ours" and "theirs". The user is supposed to run
		 * step 7 on every ref separately and not trust "ours"
		 * and "theirs" any more.
		 */
	} else
		post_assign_shallow(info, &pi.ref_bitmap, ref_status);

	clear_ref_bitmap(&pi.ref_bitmap);
	for (i = 0; i < pi.slab_count; i++)
		free(pi.slab[i]);
	free(pi.slab);
	free(shallow);
}

struct commit_array {
	struct commit **commits;
	int nr, alloc;
};

static int add_ref(const char *refname,
		   const unsigned char *sha1, int flags, void *cb_data)
{
	struct commit_array *ca = cb_data;
	ALLOC_GROW(ca->commits, ca->nr + 1, ca->alloc);
	ca->commits[ca->nr] = lookup_commit_reference_gently(sha1, 1);
	if (ca->commits[ca->nr])
		ca->nr++;
	return 0;
}

static void update_refstatus(int *ref_status, int nr, uint32_t *bitmap)
{
	int i;
	if (!ref_status)
		return;
	for (i = 0; i < nr; i++)
		if (bitmap[i / 32] & (1 << (i % 32)))
			ref_status[i]++;
}

/*
 * Step 7, reachability test on "ours" at commit level
 */
static void post_assign_shallow(struct shallow_info *info,
				struct ref_bitmap *ref_bitmap,
				int *ref_status)
{
	unsigned char (*sha1)[20] = info->shallow->sha1;
	struct commit *c;
	uint32_t **bitmap;
	int dst, i, j;
	int bitmap_nr = (info->ref->nr + 31) / 32;
	struct commit_array ca;

	trace_printf_key(TRACE_KEY, "shallow: post_assign_shallow\n");
	if (ref_status)
		memset(ref_status, 0, sizeof(*ref_status) * info->ref->nr);

	/* Remove unreachable shallow commits from "theirs" */
	for (i = dst = 0; i < info->nr_theirs; i++) {
		if (i != dst)
			info->theirs[dst] = info->theirs[i];
		c = lookup_commit(sha1[info->theirs[i]]);
		bitmap = ref_bitmap_at(ref_bitmap, c);
		if (!*bitmap)
			continue;
		for (j = 0; j < bitmap_nr; j++)
			if (bitmap[0][j]) {
				update_refstatus(ref_status, info->ref->nr, *bitmap);
				dst++;
				break;
			}
	}
	info->nr_theirs = dst;

	memset(&ca, 0, sizeof(ca));
	head_ref(add_ref, &ca);
	for_each_ref(add_ref, &ca);

	/* Remove unreachable shallow commits from "ours" */
	for (i = dst = 0; i < info->nr_ours; i++) {
		if (i != dst)
			info->ours[dst] = info->ours[i];
		c = lookup_commit(sha1[info->ours[i]]);
		bitmap = ref_bitmap_at(ref_bitmap, c);
		if (!*bitmap)
			continue;
		for (j = 0; j < bitmap_nr; j++)
			if (bitmap[0][j] &&
			    /* Step 7, reachability test at commit level */
			    !in_merge_bases_many(c, ca.nr, ca.commits)) {
				update_refstatus(ref_status, info->ref->nr, *bitmap);
				dst++;
				break;
			}
	}
	info->nr_ours = dst;

	free(ca.commits);
}