Walk a path on the blob page from any commit the id names

With both an id and a path the blob page handed back the raw object
the id named, so a commit id gave the commit text itself, while the
plain page looked the path up in that commit's tree. A tag is peeled
to its commit on the way, and the README example of a pinned commit
now uses a form the request checks accept.

1 file changed, 13 insertions, 7 deletions

diff --git a/source/ui-blob.c b/source/ui-blob.c
index 8407342..4105e48 100644
--- a/source/ui-blob.c
+++ b/source/ui-blob.c
@@ -181,17 +181,23 @@ void cgit_print_blob(const char *hex, char *path, const char *head, int file_onl
 			cgit_print_error_page(404, "Not Found", "Bad object id: %s", hex);
 			return;
 		}
-	} else {
-		if (repo_get_oid(the_repository, head, &oid)) {
-			cgit_print_error_page(404, "Not Found", "Bad object id: %s", head);
-			return;
-		}
-		peel_to_commit(&oid);
+	} else if (repo_get_oid(the_repository, head, &oid)) {
+		cgit_print_error_page(404, "Not Found", "Bad object id: %s", head);
+		return;
 	}
 
 	type = odb_read_object_info(the_repository->objects, &oid, &size);
 
-	if (!hex && type == OBJ_COMMIT && path) {
+	// A tag is peeled to its commit, so a path can be looked up in the
+	// tree whether the id or the head named the tag. The type is read
+	// first because peeling a blob would read it whole just to learn that
+	// it is one.
+	if (type == OBJ_TAG) {
+		peel_to_commit(&oid);
+		type = odb_read_object_info(the_repository->objects, &oid, &size);
+	}
+
+	if (type == OBJ_COMMIT && path) {
 		if (!find_path_oid(&oid, path, file_only)) {
 			cgit_print_error_page(404, "Not Found", "Path not found: %s", path);
 			return;