blame: handle error when resoling HEAD in normalize_options

When normalizing options we try to look up HEAD's OID. While this
action may fail in malformed repositories we never check the
return value of the function.

Fix the issue by converting `normalize_options` to actually
return an error and handle the error in `git_blame_file`.

src/blame.c

@@ -178,7 +178,7 @@ const git_blame_hunk *git_blame_get_hunk_byline(git_blame *blame, size_t lineno)
 	return NULL;
 }
 
-static void normalize_options(
+static int normalize_options(
 		git_blame_options *out,
 		const git_blame_options *in,
 		git_repository *repo)
@@ -190,7 +190,9 @@ static void normalize_options(
 
 	/* No newest_commit => HEAD */
 	if (git_oid_iszero(&out->newest_commit)) {
-		git_reference_name_to_id(&out->newest_commit, repo, "HEAD");
+		if (git_reference_name_to_id(&out->newest_commit, repo, "HEAD") < 0) {
+			return -1;
+		}
 	}
 
 	/* min_line 0 really means 1 */
@@ -204,6 +206,8 @@ static void normalize_options(
 		out->flags |= GIT_BLAME_TRACK_COPIES_SAME_COMMIT_MOVES;
 	if (out->flags & GIT_BLAME_TRACK_COPIES_SAME_COMMIT_MOVES)
 		out->flags |= GIT_BLAME_TRACK_COPIES_SAME_FILE;
+
+	return 0;
 }
 
 static git_blame_hunk *split_hunk_in_vector(
@@ -362,7 +366,8 @@ int git_blame_file(
 	git_blame *blame = NULL;
 
 	assert(out && repo && path);
-	normalize_options(&normOptions, options, repo);
+	if ((error = normalize_options(&normOptions, options, repo)) < 0)
+		goto on_error;
 
 	blame = git_blame__alloc(repo, normOptions, path);
 	GITERR_CHECK_ALLOC(blame);