Backport locate-dominating-file to Emacs22 if needed.

dominating-file.el

@@ -0,0 +1,44 @@
+;; Port this functionality back from Emacs 23 since it's Really Useful
+
+(unless (functionp 'locate-dominating-file)
+  (defun locate-dominating-file (file name)
+    "Look up the directory hierarchy from FILE for a file named NAME.
+Stop at the first parent directory containing a file NAME,
+and return the directory.  Return nil if not found."
+    ;; We used to use the above locate-dominating-files code, but the
+    ;; directory-files call is very costly, so we're much better off doing
+    ;; multiple calls using the code in here.
+    ;;
+    ;; Represent /home/luser/foo as ~/foo so that we don't try to look for
+    ;; `name' in /home or in /.
+    (setq file (abbreviate-file-name file))
+    (let ((root nil)
+          (prev-file file)
+          ;; `user' is not initialized outside the loop because
+          ;; `file' may not exist, so we may have to walk up part of the
+          ;; hierarchy before we find the "initial UID".
+          (user nil)
+          try)
+      (while (not (or root
+                      (null file)
+                      ;; FIXME: Disabled this heuristic because it is sometimes
+                      ;; inappropriate.
+                      ;; As a heuristic, we stop looking up the hierarchy of
+                      ;; directories as soon as we find a directory belonging
+                      ;; to another user.  This should save us from looking in
+                      ;; things like /net and /afs.  This assumes that all the
+                      ;; files inside a project belong to the same user.
+                      ;; (let ((prev-user user))
+                      ;;   (setq user (nth 2 (file-attributes file)))
+                      ;;   (and prev-user (not (equal user prev-user))))
+                      (string-match locate-dominating-stop-dir-regexp file)))
+        (setq try (file-exists-p (expand-file-name name file)))
+        (cond (try (setq root file))
+              ((equal file (setq prev-file file
+                                 file (file-name-directory
+                                       (directory-file-name file))))
+               (setq file nil))))
+      root))
+
+  (defvar locate-dominating-stop-dir-regexp
+    "\\`\\(?:[\\/][\\/][^\\/]+\\|/\\(?:net\\|afs\\|\\.\\.\\.\\)/\\)\\'"))

init.el

@@ -32,6 +32,9 @@
 (require 'ansi-color)
 (require 'recentf)
 
+;; backport some functionality to Emacs 22 if needed
+(require 'dominating-file)
+
 ;; this must be loaded before ELPA since it bundles its own
 ;; out-of-date js stuff. TODO: fix it to use ELPA dependencies
 (load "elpa-to-submit/nxhtml/autostart")