commit-graph: verify objects exist

In the 'verify' subcommand, load commits directly from the object
database to ensure they exist. Parse by skipping the commit-graph.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit-graph.c

@@ -11,6 +11,7 @@
 #include "sha1-lookup.h"
 #include "commit-graph.h"
 #include "object-store.h"
+#include "alloc.h"
 
 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
 #define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
@@ -242,6 +243,7 @@ static struct commit_list **insert_parent_or_die(struct commit_graph *g,
 {
 	struct commit *c;
 	struct object_id oid;
+
 	hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
 	c = lookup_commit(&oid);
 	if (!c)
@@ -893,5 +895,21 @@ int verify_commit_graph(struct repository *r, struct commit_graph *g)
 		cur_fanout_pos++;
 	}
 
+	if (verify_commit_graph_error)
+		return verify_commit_graph_error;
+
+	for (i = 0; i < g->num_commits; i++) {
+		struct commit *odb_commit;
+
+		hashcpy(cur_oid.hash, g->chunk_oid_lookup + g->hash_len * i);
+
+		odb_commit = (struct commit *)create_object(r, cur_oid.hash, alloc_commit_node(r));
+		if (parse_commit_internal(odb_commit, 0, 0)) {
+			graph_report("failed to parse %s from object database",
+				     oid_to_hex(&cur_oid));
+			continue;
+		}
+	}
+
 	return verify_commit_graph_error;
 }

t/t5318-commit-graph.sh

@@ -247,6 +247,7 @@ test_expect_success 'git commit-graph verify' '
 	git commit-graph verify >output
 '
 
+NUM_COMMITS=9
 HASH_LEN=20
 GRAPH_BYTE_VERSION=4
 GRAPH_BYTE_HASH=5
@@ -265,6 +266,7 @@ GRAPH_BYTE_FANOUT1=$(($GRAPH_FANOUT_OFFSET + 4 * 4))
 GRAPH_BYTE_FANOUT2=$(($GRAPH_FANOUT_OFFSET + 4 * 255))
 GRAPH_OID_LOOKUP_OFFSET=$(($GRAPH_FANOUT_OFFSET + 4 * 256))
 GRAPH_BYTE_OID_LOOKUP_ORDER=$(($GRAPH_OID_LOOKUP_OFFSET + $HASH_LEN * 8))
+GRAPH_BYTE_OID_LOOKUP_MISSING=$(($GRAPH_OID_LOOKUP_OFFSET + $HASH_LEN * 4 + 10))
 
 # usage: corrupt_graph_and_verify <position> <data> <string>
 # Manipulates the commit-graph file at the position
@@ -334,4 +336,9 @@ test_expect_success 'detect incorrect OID order' '
 		"incorrect OID order"
 '
 
+test_expect_success 'detect OID not in object database' '
+	corrupt_graph_and_verify $GRAPH_BYTE_OID_LOOKUP_MISSING "\01" \
+		"from object database"
+'
+
 test_done