bloom: parse commit before computing filters

When computing changed-path Bloom filters for a commit, we need to
know if the commit has a parent or not. If the commit is not parsed,
then its parent pointer will be NULL.

As far as I can tell, the only opportunity to reach this code
without parsing the commit is inside "test-tool bloom
get_filter_for_commit" but it is best to be safe.

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

bloom.c

@@ -193,6 +193,9 @@ struct bloom_filter *get_bloom_filter(struct repository *r,
 	diffopt.max_changes = max_changes;
 	diff_setup_done(&diffopt);
 
+	/* ensure commit is parsed so we have parent information */
+	repo_parse_commit(r, c);
+
 	if (c->parents)
 		diff_tree_oid(&c->parents->item->object.oid, &c->object.oid, "", &diffopt);
 	else