Re: Proposal: diff-remove-trailing-blanks

[Vinicius Jose Latorre]

> > > > What relevant things would you like to see (or to be done) in a diff buffer?
> > > >     
> > > Here, we are interested on parts of the buffer, we don't care much about
> > > trailing whitespace out of the diff part that shows changed lines. That
> > > is, we are not interested on trailing whitespace on context lines, nor
> > > on those that are artifacts of diff-mode.
> > >   
> > Hummm, I'm confused, the original mail said:
> >
> >  "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."
> >
> >
> > So, I thought it was to remove trailing whitespaces from a diff buffer.
>
> The "removing" part is accomplished by my function. We are discussing
> the "displaying" part, which shows to the user that there is trailing
> whitespace to be removed.
>
> But I'm afraid I confused things out relating `show-trailing-whitespace'
> to whitespace-mode'.

Well, both parts, the "removing" part and the "displaying" part, related 
with trailing whitespaces can be done by whitespace-mode.

Does the following function do the job?

(defun diff-remove-trailing-blanks ()
 "When on a buffer that contains a diff, inspects the
differences and removes trailing whitespace (spaces, tabs).
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))
 ;; We assume that the diff header has no trailing whitespace.
 (let (modified-buffers)
   (while (re-search-forward "^[+!>].*[ \t]+$" (point-max) t)
     (save-excursion
   (destructuring-bind (buf line-offset pos src dst &optional switched)
           (diff-find-source-location t t)
         (unless (member buf modified-buffers)
           (when line-offset
             (set-buffer buf)
             (when (re-search-forward "\\([ \t]+\\)$" (point-max) t)
               (push buf modified-buffers)
               (let ((whitespace-style '(trailing)))
                 (whitespace-cleanup)))))))) ; cleanup trailing blanks 
in buf
   (if modified-buffers
       (let ((bufs (mapconcat #(lambda (buf)
                                 (format "`%s'" (buffer-name buf)))
                              modified-buffers
                              " "))
             (whitespace-style '(trailing)))
         (whitespace-mode)           ; display trailing blanks in diff 
buffer
         (message "Deleted trailing whitespace from: %s" bufs))
     (message "No fixes needed."))))


> > What are the relevant parts of the buffer?
>
> Those that correspond to added or modified lines in the diff.

So, should lines beginning with +, - and ! have a face to display the 
change?