GNU bug report logs - #14989
24.3.50; log-view-diff and log-view-diff-changeset default to different `to' revisions for git merge commits

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#14989: closed (24.3.50; log-view-diff and log-view-diff-changeset
 default to different `to' revisions for git merge commits)
Date: Wed, 31 Jul 2013 12:28:03 +0000

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Your message dated Wed, 31 Jul 2013 15:26:45 +0300
with message-id <51F90285.9050702 <at> yandex.ru>
and subject line Re: bug#14989: 24.3.50; log-view-diff and log-view-diff-changeset default to different `to' revisions for git merge commits
has caused the debbugs.gnu.org bug report #14989,
regarding 24.3.50; log-view-diff and log-view-diff-changeset default to different `to' revisions for git merge commits
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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14989: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=14989
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From: Dmitry Gutov <dgutov <at> yandex.ru>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.50;
 log-view-diff and log-view-diff-changeset default to different `to'
 revisions for git merge commits
Date: Wed, 31 Jul 2013 01:42:57 +0300

To reproduce:

Have a merge commit where the second branch (merged from) has a newer
last commit than the first branch (merged to).

`vc-print-root-log' buffer would look like this:

*  (HEAD, devel)b044fba..: Some Guy 2013-07-25 foo foo
*   2152d76..: Dmitry Gutov 2013-07-25 Merge branch 'bar' into devel
|\
| *  (bar)1554943..: Another Guy 2013-07-25 Abc
| * f92770a..: Another Guy 2013-07-25 Def
* | 5f5c068..: Another Guy 2013-07-25 Ghi

If I move to commit 2152d76 and press `d', it will show the diff against
1554943. If I press `D', if will show the diff against 5f5c068, which is
*the* parent commit, as far as Git is concerned (the first parent, to be
more exact), because it belongs to the branch `devel', and the merge was
done from `bar' to `devel'.

Since this is a `vc-print-root-log' buffer, both commands will show the
full changesets, not just changes in an individual file.

But the behavior in `vc-print-log' is the same in this respect, except
the diff `d' shows is just for the current file.

`log-view-diff' behavior makes certain amount of sense (it always diffs
against the revision on the line below), but it's inconsistent with
`log-view-diff-changeset', and it also backfires when the current commit
is not a child of the commit on the previous line. Example: f92770a and
5f5c068. As a result, we get a meaningless diff.

This fix is simple enough. Apply?

=== modified file 'lisp/vc/log-view.el'
--- lisp/vc/log-view.el 2013-06-11 06:36:06 +0000
+++ lisp/vc/log-view.el 2013-07-30 22:31:40 +0000
@@ -565,10 +565,7 @@
   (let ((fr (log-view-current-tag beg))
         (to (log-view-current-tag end)))
     (when (string-equal fr to)
-      (save-excursion
-        (goto-char end)
-        (log-view-msg-next)
-        (setq to (log-view-current-tag))))
+      (setq to (vc-call-backend log-view-vc-backend 'previous-revision nil fr)))
     (vc-diff-internal
      t (list log-view-vc-backend
             (if log-view-per-file-logs

The functions could also use some further cleanup:
1) Swap the `to' and `fr' local variables.
2) Extract the function bodies to one function with a third argument
(called `whole-changeset', maybe), and make them call it.

Objections?

[Message part 3 (message/rfc822, inline)]

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 14989-done <at> debbugs.gnu.org
Subject: Re: bug#14989: 24.3.50; log-view-diff and log-view-diff-changeset
 default to different `to' revisions for git merge commits
Date: Wed, 31 Jul 2013 15:26:45 +0300

Done!

On 31.07.2013 04:38, Stefan Monnier wrote:
>> This fix is simple enough. Apply?
>
> Looks good, thanks.
>
>> The functions could also use some further cleanup:
>> 1) Swap the `to' and `fr' local variables.
>
> I think that would make sense, yes.
>
>> 2) Extract the function bodies to one function with a third argument
>> (called `whole-changeset', maybe), and make them call it.
>
> If that can be done without too much extra code, that sounds good.

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