* vc/diff-mode.el (diff-remove-trailing-whitespace): New function.

2 files changed, 45 insertions, 0 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 9a94a37af69..479fee02027 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2012-08-08  Óscar Fuentes  <ofv@wanadoo.es>
+
+        * vc/diff-mode.el (diff-remove-trailing-whitespace): New function.
+
 2012-08-08  Fabián Ezequiel Gallina  <fgallina@cuca>
 
         * progmodes/python.el Fixed defsubst warning.
diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index a9d124700b8..d3d9878c5ad 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -2016,6 +2016,47 @@ I.e. like `add-change-log-entry-other-window' but applied to all hunks."
       ;; When there's no more hunks, diff-hunk-next signals an error.
       (error nil))))
 
+(defun diff-remove-trailing-whitespace ()
+  "When on a buffer that contains a diff, inspects the
+differences and removes trailing whitespace (spaces, tabs) from
+the lines modified or introduced by this diff. Shows a message
+with the name of the altered buffers, which are unsaved.  If a
+file referenced on the diff has no buffer and needs to be fixed,
+a buffer visiting that file is created."
+  (interactive)
+  (goto-char (point-min))
+  (let
+      ;; We assume that the diff header has no trailing whitespace.
+      ((modified-buffers nil)
+       (white-positions nil))
+    (while (re-search-forward "^[+!>].*[ \t]+$" (point-max) t)
+      (save-excursion
+        (cl-destructuring-bind (buf line-offset pos src _dst &optional _switched)
+            (diff-find-source-location t t)
+          (when line-offset
+            (set-buffer buf)
+            (save-excursion
+              (goto-char (+ (car pos) (cdr src)))
+              (beginning-of-line)
+              (when (re-search-forward "\\([ \t]+\\)$" (line-end-position) t)
+                (when (not (member buf modified-buffers))
+                  (push buf modified-buffers))
+                (goto-char (match-end 0))
+                (push (point-marker) white-positions)
+                (goto-char (match-beginning 0))
+                (push (point-marker) white-positions)
+                (push buf white-positions)))))))
+    (while white-positions
+      (save-excursion
+        (set-buffer (pop white-positions))
+        (delete-region (pop white-positions) (pop white-positions))))
+    (if modified-buffers
+        (let ((msg "Deleted new trailing whitespace from:"))
+          (dolist (f modified-buffers)
+            (setq msg (concat msg " `" (buffer-name f) "'")))
+          (message "%s" msg))
+      (message "No trailing whitespace fixes needed."))))
+
 ;; provide the package
 (provide 'diff-mode)