[PATCH v2 13/14] commit-graph: close under reachability

[Derrick Stolee <stolee@gmail.com>]

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

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c          | 26 ++++++++++++++++++++++++++
 t/t5318-commit-graph.sh | 14 ++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/commit-graph.c b/commit-graph.c
index e5a1d9ee8b..cfa0415a21 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -5,6 +5,7 @@
 #include "packfile.h"
 #include "commit.h"
 #include "object.h"
+#include "revision.h"
 #include "commit-graph.h"
 
 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
@@ -638,6 +639,29 @@ 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->num; 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->num + 1, oids->size);
+		oids->list[oids->num] = &(commit->object.oid);
+		(oids->num)++;
+	}
+}
+
 struct object_id *construct_commit_graph(const char *pack_dir,
 					 char **pack_indexes,
 					 int nr_packs)
@@ -696,6 +720,8 @@ struct object_id *construct_commit_graph(const char *pack_dir,
 	} else {
 		for_each_packed_object(if_packed_commit_add_to_list, &oids, 0);
 	}
+
+	close_reachable(&oids);
 	QSORT(oids.list, oids.num, commit_compare);
 
 	count_distinct = 1;
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index b9a73f398c..2001b0b5b5 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -213,6 +213,20 @@ test_expect_success 'clear graph' \
 _graph_git_behavior commits/20 merge/1
 _graph_git_behavior commits/20 merge/2
 
+test_expect_success 'build graph from latest pack with closure' \
+    'graph5=$(cat new-idx | git commit-graph --write --update-head --stdin-packs) &&
+     test_path_is_file ${packdir}/graph-${graph5}.graph &&
+     test_path_is_file ${packdir}/graph-${graph1}.graph &&
+     test_path_is_file ${packdir}/graph-head &&
+     echo ${graph5} >expect &&
+     cmp -n 40 expect ${packdir}/graph-head &&
+     git commit-graph --read --graph-hash=${graph5} >output &&
+     _graph_read_expect "21" "${packdir}" &&
+     cmp expect output'
+
+_graph_git_behavior commits/20 merge/1
+_graph_git_behavior commits/20 merge/2
+
 test_expect_success 'setup bare repo' \
     'cd .. &&
      git clone --bare full bare &&
-- 
2.16.0.15.g9c3cf44.dirty