(file-truename): Don't use expand-file-name to merge

a link target into the previous dir.  Handle .. and . explicitly.

1 files changed, 19 insertions, 10 deletions

diff --git a/lisp/files.el b/lisp/files.el
index c31b75e1ce6..96cc510a61c 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -329,16 +329,25 @@ containing it, until no links are left at any level."
         ;; If these are equal, we have the (or a) root directory.
         (or (string= dir dirfile)
             (setq dir (file-name-as-directory (file-truename dirfile))))
-        ;; Put it back on the file name.
-        (setq filename (concat dir (file-name-nondirectory filename)))
-        ;; Is the file name the name of a link?
-        (setq target (file-symlink-p filename))
-        (if target
-            ;; Yes => chase that link, then start all over
-            ;; since the link may point to a directory name that uses links.
-            (file-truename (expand-file-name target dir))
-          ;; No, we are done!
-          filename)))))
+        (if (equal ".." (file-name-nondirectory filename))
+            (directory-file-name (file-name-directory (directory-file-name dir)))
+          (if (equal "." (file-name-nondirectory filename))
+              (directory-file-name dir)
+            ;; Put it back on the file name.
+            (setq filename (concat dir (file-name-nondirectory filename)))
+            ;; Is the file name the name of a link?
+            (setq target (file-symlink-p filename))
+            (if target
+                ;; Yes => chase that link, then start all over
+                ;; since the link may point to a directory name that uses links.
+                ;; We can't safely use expand-file-name here
+                ;; since target might look like foo/../bar where foo
+                ;; is itself a link.  Instead, we handle . and .. above.
+                (if (file-name-absolute-p target)
+                    (file-truename target)
+                  (file-truename (concat dir target)))
+              ;; No, we are done!
+              filename)))))))
 
 (defun file-chase-links (filename)
   "Chase links in FILENAME until a name that is not a link.