[PATCH v3 12/14] commit-graph: close under reachability

[Derrick Stolee <stolee@gmail.com>]

Teach write_commit_graph() to walk all parents from the commits
discovered in packfiles. This prevents gaps given by loose objects or
previously-missed packfiles.

Also automatically add commits from the existing graph file, if it
exists.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/commit-graph.c b/commit-graph.c
index aff67c458e..d711a2cd81 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -633,6 +633,28 @@ static int if_packed_commit_add_to_list(const struct object_id *oid,
 	return 0;
 }
 
+static void close_reachable(struct packed_oid_list *oids)
+{
+	int i;
+	struct rev_info revs;
+	struct commit *commit;
+	init_revisions(&revs, NULL);
+	for (i = 0; i < oids->nr; i++) {
+		commit = lookup_commit(oids->list[i]);
+		if (commit && !parse_commit(commit))
+			revs.commits = commit_list_insert(commit, &revs.commits);
+	}
+
+	if (prepare_revision_walk(&revs))
+		die(_("revision walk setup failed"));
+
+	while ((commit = get_revision(&revs)) != NULL) {
+		ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
+		oids->list[oids->nr] = &(commit->object.oid);
+		(oids->nr)++;
+	}
+}
+
 struct object_id *write_commit_graph(const char *pack_dir)
 {
 	struct packed_oid_list oids;
@@ -650,12 +672,27 @@ struct object_id *write_commit_graph(const char *pack_dir)
 	char *fname;
 	struct commit_list *parent;
 
+	prepare_commit_graph();
+
 	oids.nr = 0;
 	oids.alloc = 1024;
+
+	if (commit_graph && oids.alloc < commit_graph->num_commits)
+		oids.alloc = commit_graph->num_commits;
+
 	ALLOC_ARRAY(oids.list, oids.alloc);
 
+	if (commit_graph) {
+		for (i = 0; i < commit_graph->num_commits; i++) {
+			oids.list[i] = malloc(sizeof(struct object_id));
+			get_nth_commit_oid(commit_graph, i, oids.list[i]);
+		}
+		oids.nr = commit_graph->num_commits;
+	}
+
 	for_each_packed_object(if_packed_commit_add_to_list, &oids, 0);
 
+	close_reachable(&oids);
 	QSORT(oids.list, oids.nr, commit_compare);
 
 	count_distinct = 1;
-- 
2.15.1.45.g9b7079f