1 file changed, 6 insertions, 20 deletions
diff --git a/source/ui-diff.c b/source/ui-diff.c
index 736cdaf..51df73d 100644
--- a/source/ui-diff.c
+++ b/source/ui-diff.c
@@ -604,31 +604,17 @@ void cgit_print_diff(const char *new_rev, const char *old_rev, const char *prefi
 
 	if (!new_rev)
 		new_rev = ctx.qry.head;
-	if (repo_get_oid(the_repository, new_rev, new_rev_oid)) {
-		cgit_print_error_page(404, "Not Found", "Bad object id: %s", new_rev);
+	new_commit = cgit_get_commit(new_rev, new_rev_oid);
+	if (!new_commit || cgit_get_old_oid(old_rev, new_commit, old_rev_oid))
 		return;
-	}
-	new_commit = lookup_commit_reference(the_repository, new_rev_oid);
-	if (!new_commit || repo_parse_commit(the_repository, new_commit)) {
-		cgit_print_error_page(404, "Not Found", "Not a commit: %s", oid_to_hex(new_rev_oid));
-		return;
-	}
 	new_tree_oid = get_commit_tree_oid(new_commit);
 
-	if (old_rev) {
-		if (repo_get_oid(the_repository, old_rev, old_rev_oid)) {
-			cgit_print_error_page(404, "Not Found", "Bad object id: %s", old_rev);
-			return;
-		}
-	} else if (new_commit->parents && new_commit->parents->item) {
-		oidcpy(old_rev_oid, &new_commit->parents->item->object.oid);
-	} else {
-		oidclr(old_rev_oid, the_repository->hash_algo);
-	}
-
 	if (!is_null_oid(old_rev_oid)) {
+		// A named old side is a commit already, so only a first parent
+		// missing from the repository fails here, and it has no name
+		// but its id.
 		old_commit = lookup_commit_reference(the_repository, old_rev_oid);
-		if (!old_commit || repo_parse_commit(the_repository, old_commit)) {
+		if (!old_commit) {
 			cgit_print_error_page(404, "Not Found", "Not a commit: %s", oid_to_hex(old_rev_oid));
 			return;
 		}