commit-graph: verify required chunks are present

The commit-graph file requires the following three chunks:

* OID Fanout
* OID Lookup
* Commit Data

If any of these are missing, then the 'verify' subcommand should
report a failure. This includes the chunk IDs malformed or the
chunk count is truncated.

Signed-off-by: Derrick Stolee <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: derrickstolee

commit-graph.c

@@ -848,5 +848,14 @@ int verify_commit_graph(struct repository *r, struct commit_graph *g)
 		return 1;
 	}
 
+	verify_commit_graph_error = 0;
+
+	if (!g->chunk_oid_fanout)
+		graph_report("commit-graph is missing the OID Fanout chunk");
+	if (!g->chunk_oid_lookup)
+		graph_report("commit-graph is missing the OID Lookup chunk");
+	if (!g->chunk_commit_data)
+		graph_report("commit-graph is missing the Commit Data chunk");
+
 	return verify_commit_graph_error;
 }

t/t5318-commit-graph.sh

@@ -249,6 +249,15 @@ test_expect_success 'git commit-graph verify' '
 
 GRAPH_BYTE_VERSION=4
 GRAPH_BYTE_HASH=5
+GRAPH_BYTE_CHUNK_COUNT=6
+GRAPH_CHUNK_LOOKUP_OFFSET=8
+GRAPH_CHUNK_LOOKUP_WIDTH=12
+GRAPH_CHUNK_LOOKUP_ROWS=5
+GRAPH_BYTE_OID_FANOUT_ID=$GRAPH_CHUNK_LOOKUP_OFFSET
+GRAPH_BYTE_OID_LOOKUP_ID=$(($GRAPH_CHUNK_LOOKUP_OFFSET + \
+			    1 * $GRAPH_CHUNK_LOOKUP_WIDTH))
+GRAPH_BYTE_COMMIT_DATA_ID=$(($GRAPH_CHUNK_LOOKUP_OFFSET + \
+			     2 * $GRAPH_CHUNK_LOOKUP_WIDTH))
 
 # usage: corrupt_graph_and_verify <position> <data> <string>
 # Manipulates the commit-graph file at the position
@@ -283,4 +292,24 @@ test_expect_success 'detect bad hash version' '
 		"hash version"
 '
 
+test_expect_success 'detect low chunk count' '
+	corrupt_graph_and_verify $GRAPH_BYTE_CHUNK_COUNT "\02" \
+		"missing the .* chunk"
+'
+
+test_expect_success 'detect missing OID fanout chunk' '
+	corrupt_graph_and_verify $GRAPH_BYTE_OID_FANOUT_ID "\0" \
+		"missing the OID Fanout chunk"
+'
+
+test_expect_success 'detect missing OID lookup chunk' '
+	corrupt_graph_and_verify $GRAPH_BYTE_OID_LOOKUP_ID "\0" \
+		"missing the OID Lookup chunk"
+'
+
+test_expect_success 'detect missing commit data chunk' '
+	corrupt_graph_and_verify $GRAPH_BYTE_COMMIT_DATA_ID "\0" \
+		"missing the Commit Data chunk"
+'
+
 test_done