Code and doc fixes for file-subdir-of-p and files-equal-p.

* lisp/files.el (files-equal-p): Doc fix.
(file-subdir-of-p): Doc fix.  Convert loop macro to plain Lisp,
and quit the loop once a mismatch is found.

* doc/lispref/files.texi (Kinds of Files): Improve documentation of
files-equal-p and file-subdir-of-p.

2 files changed, 25 insertions, 16 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index f585be4ec34..418be2539b6 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2012-02-26  Chong Yidong  <cyd@gnu.org>
+
+        * files.el (files-equal-p): Doc fix.
+        (file-subdir-of-p): Doc fix.  Convert loop macro to plain Lisp,
+        and quit the loop once a mismatch is found.
+
 2012-02-25  Juanma Barranquero  <lekktu@gmail.com>
 
         * bs.el (bs--show-with-configuration): Don't throw an error
diff --git a/lisp/files.el b/lisp/files.el
index 3523fbdc012..acd04de34ec 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -4986,7 +4986,9 @@ given.  With a prefix argument, TRASH is nil."
       (delete-directory-internal directory)))))
 
 (defun files-equal-p (file1 file2)
-  "Return non-nil if FILE1 and FILE2 name the same file."
+  "Return non-nil if FILE1 and FILE2 name the same file.
+Ordinary files are considered to be the same if `file-attributes'
+returns `equal' values for them."
   (let ((handler (or (find-file-name-handler file1 'files-equal-p)
                      (find-file-name-handler file2 'files-equal-p))))
     (if handler
@@ -4996,27 +4998,28 @@ given.  With a prefix argument, TRASH is nil."
 
 (defun file-subdir-of-p (dir1 dir2)
   "Return non-nil if DIR1 is a subdirectory of DIR2.
-Note that a directory is treated by this function as a subdirectory of itself.
-This function only works when its two arguments already exist,
-when they don't, it returns nil."
+A directory is considered to be a subdirectory of itself.
+Return nil if DIR1 or DIR2 are not existing directories."
   (let ((handler (or (find-file-name-handler dir1 'file-subdir-of-p)
                      (find-file-name-handler dir2 'file-subdir-of-p))))
     (if handler
         (funcall handler 'file-subdir-of-p dir1 dir2)
       (when (and (file-directory-p dir1)
                  (file-directory-p dir2))
-        (loop with f1 = (file-truename dir1)
-              with f2 = (file-truename dir2)
-              with ls1 = (or (split-string f1 "/" t) (list "/"))
-              with ls2 = (or (split-string f2 "/" t) (list "/"))
-              for p = (string-match "^/" f1)
-              for i in ls1
-              for j in ls2
-              when (string= i j)
-              concat (if p (concat "/" i) (concat i "/"))
-              into root
-              finally return
-              (files-equal-p (file-truename root) f2))))))
+        (setq dir1 (file-truename dir1)
+              dir2 (file-truename dir2))
+        (let ((ls1  (or (split-string dir1 "/" t) '("/")))
+              (ls2  (or (split-string dir2 "/" t) '("/")))
+              (root (if (string-match "\\`/" dir1) "/" ""))
+              (mismatch nil))
+          (while (and ls1 ls2 (not mismatch))
+            (if (string-equal (car ls1) (car ls2))
+                (setq root (concat root (car ls1) "/"))
+              (setq mismatch t))
+            (setq ls1 (cdr ls1)
+                  ls2 (cdr ls2)))
+          (unless mismatch
+            (files-equal-p (file-truename root) dir2)))))))
 
 (defun copy-directory (directory newname &optional keep-time parents copy-contents)
   "Copy DIRECTORY to NEWNAME.  Both args must be strings.