bug#62731: 29.0.60; diff-apply-hunk doesn't work for creating new files

[Dmitry Gutov]

Hi Juri,

On 15/10/2024 19:13, Juri Linkov wrote:
> > > All right, the attached seems to support both creation and deletion,
> > > including applying hunks in reverse direction.
> > > Things got trickier but not by a lot.
> >
> > Now pushed to master, seems useful enough. Let's see if some unforeseen
> > problems are reported.
>
> This change broke diff of files:
>
> @@ -1957,7 +1970,7 @@ diff-find-source-location
>                                   diff-context-mid-hunk-header-re nil t)
>                          (error "Can't find the hunk separator"))
>                        (match-string 1)))))
> -          (file (or (diff-find-file-name other noprompt)
> +          (file (or (diff-find-file-name (xor other reverse) noprompt)
>                        (error "Can't find the file")))
>            (revision (and other diff-vc-backend
>                             (if reverse (nth 1 diff-vc-revisions)
>
> So after 'dired-backup-diff', typing 'C-c C-c' visits wrong file:
> visits the backup when point is on the file line, and vice versa:
> visits the file when point is on backup file line.

Thanks for reporting.

Do you think we can fix it this way?

diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index cfa90d380ad..374df3ee2cb 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -2196,7 +2196,7 @@ diff-goto-source
   ;; This is a convenient detail when using smerge-diff.
   (if event (posn-set-point (event-end event)))
   (let ((buffer (when event (current-buffer)))
-        (reverse (not (save-excursion (beginning-of-line) (looking-at 
"[-<]")))))
+        (reverse (not (save-excursion (beginning-of-line) (looking-at 
"[+<]")))))
     (pcase-let ((`(,buf ,_line-offset ,pos ,src ,_dst ,_switched)
                  (diff-find-source-location other-file reverse)))
       (pop-to-buffer buf)


Otherwise, I don't quite understand the intent behind that line. But it 
might have been masking the problem which I (hopefully) fixed in the 
hunk you quoted/