receive-pack: allow pushes that update .git/shallow

The basic 8 steps to update .git/shallow does not fully apply here
because the user may choose to accept just a few refs (while fetch
always accepts all refs). The steps are modified a bit.

1-6. same as before. After calling assign_shallow_commits_to_refs at
   step 6, each shallow commit has a bitmap that marks all refs that
   require it.

7. mark all "ours" shallow commits that are reachable from any
   refs. We will need to do the original step 7 on them later.

8. go over all shallow commit bitmaps, mark refs that require new
   shallow commits.

9. setup a strict temporary shallow file to plug all the holes, even
   if it may cut some of our history short. This file is used by all
   hooks. The hooks could use --shallow-file=$GIT_DIR/shallow to
   overcome this and reach everything in current repo.

10. go over the new refs one by one. For each ref, do the reachability
   test if it needs a shallow commit on the list from step 7. Remove
   it if it's reachable from our refs. Gather all required shallow
   commits, run check_everything_connected() with the new ref, then
   install them to .git/shallow.

This mode is disabled by default and can be turned on with
receive.shallowupdate

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

1 files changed, 9 insertions, 0 deletions

diff --git a/commit.h b/commit.h
index 79649ef..a1f2d49 100644
--- a/commit.h
+++ b/commit.h
@@ -216,6 +216,14 @@ struct shallow_info {
 	int *ours, nr_ours;
 	int *theirs, nr_theirs;
 	struct sha1_array *ref;
+
+	/* for receive-pack */
+	uint32_t **used_shallow;
+	int *need_reachability_test;
+	int *reachable;
+	int *shallow_ref;
+	struct commit **commits;
+	int nr_commits;
 };
 
 extern void prepare_shallow_info(struct shallow_info *, struct sha1_array *);
@@ -226,6 +234,7 @@ extern void remove_nonexistent_ours_in_pack(struct shallow_info *,
 extern void assign_shallow_commits_to_refs(struct shallow_info *info,
 					   uint32_t **used,
 					   int *ref_status);
+extern int delayed_reachability_test(struct shallow_info *si, int c);
 
 int is_descendant_of(struct commit *, struct commit_list *);
 int in_merge_bases(struct commit *, struct commit *);