fetch: support fetching from a shallow repository

This patch just put together pieces from the 8 steps patch. We stop at
step 7 and reject refs that require new shallow commits.

Note that, by rejecting refs that require new shallow commits, we
leave dangling objects in the repo, which become "object islands" by
the next "git fetch" of the same source.

If the first fetch our "ours" set is zero and we do practically
nothing at step 7, "ours" is full at the next fetch and we may need to
walk through commits for reachability test. Room for improvement.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 30 insertions, 2 deletions

diff --git a/fetch-pack.c b/fetch-pack.c
index 6c980cd39f..34c544d0ca 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -854,7 +854,7 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	if (args->depth > 0)
 		setup_alternate_shallow(&shallow_lock, &alternate_shallow_file,
 					NULL);
-	else if (args->cloning && si->shallow && si->shallow->nr)
+	else if (si->nr_ours || si->nr_theirs)
 		alternate_shallow_file = setup_temporary_shallow(si->shallow);
 	else
 		alternate_shallow_file = NULL;
@@ -930,8 +930,11 @@ static int remove_duplicates_in_refs(struct ref **ref, int nr)
 }
 
 static void update_shallow(struct fetch_pack_args *args,
+			   struct ref **sought, int nr_sought,
 			   struct shallow_info *si)
 {
+	struct sha1_array ref = SHA1_ARRAY_INIT;
+	int *status;
 	int i;
 
 	if (args->depth > 0 && alternate_shallow_file) {
@@ -978,6 +981,31 @@ static void update_shallow(struct fetch_pack_args *args,
 		sha1_array_clear(&extra);
 		return;
 	}
+
+	if (!si->nr_ours && !si->nr_theirs)
+		return;
+
+	remove_nonexistent_theirs_shallow(si);
+	/* XXX remove_nonexistent_ours_in_pack() */
+	if (!si->nr_ours && !si->nr_theirs)
+		return;
+	for (i = 0; i < nr_sought; i++)
+		sha1_array_append(&ref, sought[i]->old_sha1);
+	si->ref = &ref;
+
+	/*
+	 * remote is also shallow, check what ref is safe to update
+	 * without updating .git/shallow
+	 */
+	status = xcalloc(nr_sought, sizeof(*status));
+	assign_shallow_commits_to_refs(si, NULL, status);
+	if (si->nr_ours || si->nr_theirs) {
+		for (i = 0; i < nr_sought; i++)
+			if (status[i])
+				sought[i]->status = REF_STATUS_REJECT_SHALLOW;
+	}
+	free(status);
+	sha1_array_clear(&ref);
 }
 
 struct ref *fetch_pack(struct fetch_pack_args *args,
@@ -1003,7 +1031,7 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 	ref_cpy = do_fetch_pack(args, fd, ref, sought, nr_sought,
 				&si, pack_lockfile);
 	reprepare_packed_git();
-	update_shallow(args, &si);
+	update_shallow(args, sought, nr_sought, &si);
 	clear_shallow_info(&si);
 	return ref_cpy;
 }