test-read-graph: include extra post-parse info

It can be helpful to verify that the 'struct commit_graph' that results
from parsing a commit-graph is correctly structured. The existence of
different chunks is not enough to verify that all of the optional
features are correctly enabled.

Update 'test-tool read-graph' to output an "options:" line that includes
information for different parts of the struct commit_graph.

In particular, this change demonstrates that the read_generation_data
option is never being enabled, which will be fixed in a later change.

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

t/t5318-commit-graph.sh

@@ -104,6 +104,7 @@ graph_read_expect() {
 	header: 43475048 1 $(test_oid oid_version) $NUM_CHUNKS 0
 	num_commits: $1
 	chunks: oid_fanout oid_lookup commit_metadata$OPTIONAL
+	options:
 	EOF
 	test-tool read-graph >output &&
 	test_cmp expect output