GNU bug report logs - #337
vc-diff forget previous point

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Ulrich Neumerkel <ulrich <at> complang.tuwien.ac.at>
To: bug-gnu-emacs <at> gnu.org
Subject: vc-diff forget previous point
Date: Sat, 31 May 2008 01:05:39 +0200

--text follows this line--

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the bug-gnu-emacs <at> gnu.org mailing list,
and to the gnu.emacs.bug news group.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

With a file under version control, I do C-x v = (vc-diff) to walk
through and resolve differences.  Since there are many, I re-issue
vc-diff to see the remaining differences.  Unfortunately, vc-diff
forgets the previous point in buffer *vc-diff* resetting point to 0.
My expectation would be that the cursor remains where it has been (not
the literal point but the corresponding part to the same source line).

Maybe something similar to C-c C-c (diff-goto-source) but in the other
direction would be useful in general.

In GNU Emacs 22.2.1 (i686-pc-linux-gnu, X toolkit)
 of 2008-05-28 on gupu.complang.tuwien.ac.at

....

Message #10 received at 337 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: 337 <at> debbugs.gnu.org
Subject: Re: bug#337: vc-diff forget previous point
Date: Tue, 03 Jun 2008 03:24:32 -0400

> With a file under version control, I do C-x v = (vc-diff) to walk
> through and resolve differences.  Since there are many, I re-issue
> vc-diff to see the remaining differences.  Unfortunately, vc-diff
> forgets the previous point in buffer *vc-diff* resetting point to 0.
> My expectation would be that the cursor remains where it has been (not
> the literal point but the corresponding part to the same source line).

> Maybe something similar to C-c C-c (diff-goto-source) but in the other
> direction would be useful in general.

Indeed.  Dan had a patch to do just that, but it was never applied and
it doesn't work any more, AFAICT.

I never applied his patch because it wasn't doing quite the right thing.
I think "The Right Thing" is to first look for the part of the diff that
refers to the current file (in case the diff includes several files),
and then within it, use a binary search with `diff-goto-source' to
figure out the position in the diff buffer that jumps closest to point.
This way, if point is within a part of the buffer where a hunk applies,
the function should be able to find the exact character position
corresponding to point, just like diff-goto-source does in the
other direction.

Patch welcome,


        Stefan

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