(file-relative-name): If FILENAME and DIRECTORY are on

different drives (on DOS/Windows) or use different handlers, do
like `expand-file-name' on FILENAME and return an absolute name.
From Lars Hansen <larsh@math.ku.dk>.

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 492b33ed13467b178119a7d1752f1f794f2becf9..17f47abc20c61b16514bc914fa469b96c545649c 100644 (file)
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,10 @@
 2003-03-29  Kai Gro\e,A_\e(Bjohann  <kai.grossjohann@gmx.net>
 
+       * files.el (file-relative-name): If FILENAME and DIRECTORY are on
+       different drives (on DOS/Windows) or use different handlers, do
+       like `expand-file-name' on FILENAME and return an absolute name.
+       From Lars Hansen <larsh@math.ku.dk>.
+
        * tramp.el: Version 2.0.31 released.
        (tramp-handle-expand-file-name): Do not allow ".." to
        cross file handler boundaries, so that "/user@host:/../foo"

diff --git a/lisp/files.el b/lisp/files.el
index 9216a6b2bf1c238dfff3354339db3f45d4a867cc..cb3da5717b940f827ddc55a14d2cbe7cb71c4ace 100644 (file)
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -2781,45 +2781,111 @@ Uses `backup-directory-alist' in the same way as does
   "Return number of names file FILENAME has."
   (car (cdr (file-attributes filename))))
 
+;; (defun file-relative-name (filename &optional directory)
+;;   "Convert FILENAME to be relative to DIRECTORY (default: `default-directory').
+;; This function returns a relative file name which is equivalent to FILENAME
+;; when used with that default directory as the default.
+;; If this is impossible (which can happen on MSDOS and Windows
+;; when the file name and directory use different drive names)
+;; then it returns FILENAME."
+;;   (save-match-data
+;;     (let ((fname (expand-file-name filename)))
+;;       (setq directory (file-name-as-directory
+;;                    (expand-file-name (or directory default-directory))))
+;;       ;; On Microsoft OSes, if FILENAME and DIRECTORY have different
+;;       ;; drive names, they can't be relative, so return the absolute name.
+;;       (if (and (or (eq system-type 'ms-dos)
+;;                (eq system-type 'cygwin)
+;;                (eq system-type 'windows-nt))
+;;            (not (string-equal (substring fname  0 2)
+;;                               (substring directory 0 2))))
+;;       filename
+;;     (let ((ancestor ".")
+;;           (fname-dir (file-name-as-directory fname)))
+;;       (while (and (not (string-match (concat "^" (regexp-quote directory)) fname-dir))
+;;                   (not (string-match (concat "^" (regexp-quote directory)) fname)))
+;;         (setq directory (file-name-directory (substring directory 0 -1))
+;;               ancestor (if (equal ancestor ".")
+;;                            ".."
+;;                          (concat "../" ancestor))))
+;;       ;; Now ancestor is empty, or .., or ../.., etc.
+;;       (if (string-match (concat "^" (regexp-quote directory)) fname)
+;;           ;; We matched within FNAME's directory part.
+;;           ;; Add the rest of FNAME onto ANCESTOR.
+;;           (let ((rest (substring fname (match-end 0))))
+;;             (if (and (equal ancestor ".")
+;;                      (not (equal rest "")))
+;;                 ;; But don't bother with ANCESTOR if it would give us `./'.
+;;                 rest
+;;               (concat (file-name-as-directory ancestor) rest)))
+;;         ;; We matched FNAME's directory equivalent.
+;;         ancestor))))))
+
 (defun file-relative-name (filename &optional directory)
   "Convert FILENAME to be relative to DIRECTORY (default: `default-directory').
 This function returns a relative file name which is equivalent to FILENAME
 when used with that default directory as the default.
-If this is impossible (which can happen on MSDOS and Windows
-when the file name and directory use different drive names)
-then it returns FILENAME."
+If FILENAME and DIRECTORY lie on different machines or on different drives
+\(DOS/Windows), it returns FILENAME in expanded form."
   (save-match-data
-    (let ((fname (expand-file-name filename)))
-      (setq directory (file-name-as-directory
-                      (expand-file-name (or directory default-directory))))
-      ;; On Microsoft OSes, if FILENAME and DIRECTORY have different
-      ;; drive names, they can't be relative, so return the absolute name.
-      (if (and (or (eq system-type 'ms-dos)
-                  (eq system-type 'cygwin)
-                  (eq system-type 'windows-nt))
-              (not (string-equal (substring fname  0 2)
-                                 (substring directory 0 2))))
+    (setq directory
+         (file-name-as-directory (expand-file-name (or directory
+                                                       default-directory))))
+    (setq filename (expand-file-name filename))
+    (let ((hf (find-file-name-handler filename 'file-local-copy))
+          (hd (find-file-name-handler directory 'file-local-copy)))
+      (when (and hf (not (get hf 'file-remote-p))) (setq hf nil))
+      (when (and hd (not (get hd 'file-remote-p))) (setq hd nil))
+      (if (and
+          ;; Conditions for separate trees
+          (or
+            ;; Test for different drives on DOS/Windows
+            (and
+            (memq system-type '(ms-dos cygwin windows-nt))
+            (not (string-equal (substring filename  0 2)
+                               (substring directory 0 2))))
+            ;; Test for different remote file handlers
+            (not (eq hf hd))
+            ;; Test for different remote file system identification
+            (and
+            hf
+            (let ((re (car (rassq hf file-name-handler-alist))))
+              (not
+               (equal
+                (and
+                 (string-match re filename)
+                 (substring filename 0 (match-end 0)))
+                (and
+                 (string-match re directory)
+                 (substring directory 0 (match-end 0)))))))))
          filename
-       (let ((ancestor ".")
-             (fname-dir (file-name-as-directory fname)))
-         (while (and (not (string-match (concat "^" (regexp-quote directory)) fname-dir))
-                     (not (string-match (concat "^" (regexp-quote directory)) fname)))
-           (setq directory (file-name-directory (substring directory 0 -1))
+        (unless (eq (aref filename 0) ?/)
+         (setq filename (concat "/" filename)))
+        (unless (eq (aref directory 0) ?/)
+         (setq directory (concat "/" directory)))
+        (let ((ancestor ".")
+             (filename-dir (file-name-as-directory filename)))
+          (while
+             (and
+              (not (string-match (concat "^" (regexp-quote directory))
+                                 filename-dir))
+              (not (string-match (concat "^" (regexp-quote directory))
+                                 filename)))
+            (setq directory (file-name-directory (substring directory 0 -1))
                  ancestor (if (equal ancestor ".")
                               ".."
                             (concat "../" ancestor))))
-         ;; Now ancestor is empty, or .., or ../.., etc.
-         (if (string-match (concat "^" (regexp-quote directory)) fname)
-             ;; We matched within FNAME's directory part.
-             ;; Add the rest of FNAME onto ANCESTOR.
-             (let ((rest (substring fname (match-end 0))))
-               (if (and (equal ancestor ".")
-                        (not (equal rest "")))
+          ;; Now ancestor is empty, or .., or ../.., etc.
+          (if (string-match (concat "^" (regexp-quote directory)) filename)
+             ;; We matched within FILENAME's directory part.
+             ;; Add the rest of FILENAME onto ANCESTOR.
+             (let ((rest (substring filename (match-end 0))))
+               (if (and (equal ancestor ".") (not (equal rest "")))
                    ;; But don't bother with ANCESTOR if it would give us `./'.
                    rest
                  (concat (file-name-as-directory ancestor) rest)))
-           ;; We matched FNAME's directory equivalent.
-           ancestor))))))
+            ;; We matched FILENAME's directory equivalent.
+            ancestor))))))
 \f
 (defun save-buffer (&optional args)
   "Save current buffer in visited file if modified.  Versions described below.