Re: Emacs Defect. file-relative-name fail on some MS Windows Styled Path

[Eli Zaretskii]

> Date: Sat, 30 Jun 2012 20:21:13 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > From: Xah Lee <xahlee@gmail.com>
> > Date: Sat, 30 Jun 2012 09:42:52 -0700 (PDT)
> > 
> > Emacs Defect. file-relative-name fail on some MS Windows Styled Path
> > 
> > file-relative-name doesn't work on MS Windows style path when the
> > drive letter is capitalized.
> 
> Confirmed.  Please "M-x report-emacs-bug RET".

If you can rebuild your own Emacs, here's a tentative patch:

=== modified file 'lisp/files.el'
--- lisp/files.el       2012-05-07 04:29:59 +0000
+++ lisp/files.el       2012-06-30 17:31:57 +0000
@@ -4310,7 +4310,8 @@ on a DOS/Windows machine, it returns FIL
                                                        default-directory))))
     (setq filename (expand-file-name filename))
     (let ((fremote (file-remote-p filename))
-          (dremote (file-remote-p directory)))
+          (dremote (file-remote-p directory))
+         (fold-case read-file-name-completion-ignore-case))
       (if ;; Conditions for separate trees
          (or
           ;; Test for different filesystems on DOS/Windows
@@ -4319,7 +4320,7 @@ on a DOS/Windows machine, it returns FIL
            (memq system-type '(ms-dos cygwin windows-nt))
            (or
             ;; Test for different drive letters
-            (not (eq t (compare-strings filename 0 2 directory 0 2)))
+            (not (eq t (compare-strings filename 0 2 directory 0 2 fold-case)))
             ;; Test for UNCs on different servers
             (not (eq t (compare-strings
                         (progn
@@ -4344,16 +4345,16 @@ on a DOS/Windows machine, it returns FIL
           (while (not
                  (or
                   (eq t (compare-strings filename-dir nil (length directory)
-                                         directory nil nil case-fold-search))
+                                         directory nil nil fold-case))
                   (eq t (compare-strings filename nil (length directory)
-                                         directory nil nil case-fold-search))))
+                                         directory nil nil fold-case))))
             (setq directory (file-name-directory (substring directory 0 -1))
                  ancestor (if (equal ancestor ".")
                               ".."
                             (concat "../" ancestor))))
           ;; Now ancestor is empty, or .., or ../.., etc.
           (if (eq t (compare-strings filename nil (length directory)
-                                    directory nil nil case-fold-search))
+                                    directory nil nil fold-case))
              ;; We matched within FILENAME's directory part.
              ;; Add the rest of FILENAME onto ANCESTOR.
              (let ((rest (substring filename (length directory))))