+int check_filename(const char *prefix, const char *arg)
+{
+ const char *name;
+ struct stat st;
+
+ name = prefix ? prefix_filename(prefix, strlen(prefix), arg) : arg;
+ if (!lstat(name, &st))
+ return 1; /* file exists */
+ if (errno == ENOENT || errno == ENOTDIR)
+ return 0; /* file does not exist */
+ die_errno("failed to stat '%s'", arg);
+}
+
+static void NORETURN die_verify_filename(const char *prefix, const char *arg)
+{
+ unsigned char sha1[20];
+ unsigned mode;
+ /* try a detailed diagnostic ... */
+ get_sha1_with_mode_1(arg, sha1, &mode, 0, prefix);
+ /* ... or fall back the most general message. */
+ die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
+ "Use '--' to separate paths from revisions", arg);
+
+}
+