Re: master 4803fba487 1/2: 'C-x v v' on a diff buffer commits it as a patch (bug#52349)

[Alfred M. Szmidt]

   > >     'C-x v v' on a diff buffer commits it as a patch (bug#52349)
   > 
   > Excellent!  This is going to save me a lot of work in the future.

   Bother: This is only supported for Git, which is against the spirit of
   VC, and definitely against the spirit of "C-x v v".

This is a pitty indeed.  Specially seeing that it is easy enough to
get this working for all VCSs.  Here is a hack I wrote ages ago, and
this works for just about everything, it doesn't do exactly what is
needed (e.g, this works on a single file basis) but it isn't too hard
to get that working.

===File ~/diff-commit-hunk.el===============================
;;;; diff-commit-hunk.el --- commit parts of a hunk in `diff-mode'

(require 'diff-mode)

(defun current-buffer-file-name ()
  (buffer-file-name (current-buffer)))

(defun restore-source-file ()
  (with-current-buffer (current-buffer)
    (erase-buffer)
    (insert-buffer "*diff-commit-hunk*")
    (write-file (current-buffer-file-name)))
  (remove-hook 'vc-checkin-hook 'restore-source-file))

(defmacro with-original-file (&rest body)
  "Reverts associated source file temporarily in a `diff-mode'
buffer to the latest found in VCS, executes BODY and commits the
changes back VCS."
  `(progn
     (save-excursion
       (diff-goto-source)
       (let ((buf (current-buffer)))
         (with-current-buffer (get-buffer-create "*diff-commit-hunk*")
           (erase-buffer)
           (insert-buffer buf)))
       (vc-revert-file (current-buffer-file-name)))
     ,@body
     (save-excursion
       (diff-goto-source)
       (write-file (current-buffer-file-name))
       (add-hook 'vc-checkin-hook 'restore-source-file)
       (vc-checkin (list (current-buffer-file-name))
                   (vc-backend (current-buffer-file-name))))))

;;;###autoload
(defun diff-commit-hunk ()
  "Revert associated source file to the latest version from VCS,
and apply (and commit) current hunk."
  (interactive)
  (with-original-file
   (let ((diff-advance-after-apply-hunk nil))
     (diff-apply-hunk))))

;;;###autoload
(defun diff-commit-all ()
  "Like `diff-commit-hunk', but applies all hunks in the current
diff buffer."
  (interactive)
  (with-original-file
   (goto-char (point-min))
   (diff-hunk-next)                     ;Skip header.
   (while (not (eobp))
     (diff-apply-hunk))))

(define-key diff-mode-map (kbd "s-a") #'diff-commit-hunk)
(define-key diff-mode-map (kbd "H-a") #'diff-commit-all)

;;;; diff-commit-hunk.el ends here.
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