Revert "get_sha1_basic(): corner case ambiguity fix"

This reverts 6677c4665a commit.

The misguided disambiguation has been reverted, so there is no point
testing that misfeature.

sha1_name.c

@@ -223,7 +223,7 @@ static int ambiguous_path(const char *path, int len)
 			slash = 0;
 			continue;
 		}
-		return slash;
+		break;
 	}
 	return slash;
 }