Fix file-relative-name to allow for ancestors as well as descendants.

1 files changed, 5 insertions, 11 deletions

diff --git a/lisp/files.el b/lisp/files.el
index 8eb4ff490e2..f5aad139dd1 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1382,22 +1382,16 @@ Value is a list whose car is the name for the backup file
   "Return number of names file FILENAME has."
   (car (cdr (file-attributes filename))))
 
-(defun file-relative-name-1 (directory)
-  (cond ((string= directory "/")
-         filename)
-        ((string-match (concat "^" (regexp-quote directory))
-                       filename)
-         (substring filename (match-end 0)))
-        (t
-         (file-relative-name-1
-          (file-name-directory (substring directory 0 -1))))))
-
 (defun file-relative-name (filename &optional directory)
   "Convert FILENAME to be relative to DIRECTORY (default: default-directory)."
   (setq filename (expand-file-name filename)
         directory (file-name-as-directory (expand-file-name
                                            (or directory default-directory))))
-  (file-relative-name-1 directory))
+  (let ((ancestor ""))
+    (while (not (string-match (concat "^" (regexp-quote directory)) filename))
+      (setq directory (file-name-directory (substring directory 0 -1))
+            ancestor (concat "../" ancestor)))
+    (concat ancestor (substring filename (match-end 0)))))
 
 (defun save-buffer (&optional args)
   "Save current buffer in visited file if modified.  Versions described below.