Re: ediff merge wrapper

[Eliza Velasquez <exv@google.com>]

Okay, as I mentioned in the bug thread, I have a fix working which
requires some polish before I submit a patch for it. Unfortunately,
the emacsclient command to replace the wrapper script would still be
pretty long and unwieldy:

emacsclient -ucF "((delete-frame-on-ediff-quit . t))" \
  -e "(ediff-merge-with-ancestor \"${local}\" \"${other}\" \"${base}\"
nil \"${output}\")" \
  -e "(add-hook 'ediff-quit-hook (lambda () (when (frame-parameter nil
'delete-frame-on-ediff-quit) (delete-frame))))"

I think a more robust version of this command (that could correctly
handle cases where the server is not running) could be included as
both a bash script and a Windows batch script, which could then easily
be used as an HGMERGE or P4MERGE tool.

On Tue, Nov 3, 2020 at 10:44 AM Eliza Velasquez <exv@google.com> wrote:
>
> I replied with more details about how it works, but it seems I
> accidentally sent them in a private email to Stefan. Sorry about that,
> I'm not quite used to mailing lists. I'll copy what I wrote here.
>
> Google's ediff_merge tool is invoked like:
>
> ediff_merge /path/to/base_file /path/to/ancestor /path/to/file-a
> /path/to/file-b /path/to/output-file
>
> This command blocks until the merge operation is complete, i.e. when
> the user quits ediff.
>
> Upon further investigation of its source code, it seems that the need
> for this tool may be obsoleted if this bug were to be fixed instead:
> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25547. Most of the
> purpose of this tool seems to be a workaround for this behavior, and
> it could probably be replaced with a call to `emacsclient -c -e
> '(ediff-merge-with-ancestor "$a" "$b" "$ancestor" nil "$output")'` if
> it were fixed.
>
> Stefan and I had some additional discussion on the bug thread.
>
> On Tue, Nov 3, 2020 at 8:47 AM Eli Zaretskii <eliz@gnu.org> wrote:
> >
> > > From: Eliza Velasquez <exv@google.com>
> > > Date: Mon, 2 Nov 2020 12:01:33 -0800
> > >
> > > Internally at Google, we have a wrapper performing an ediff merge with
> > > emacs/emacsclient which blocks until the merge operation has
> > > completed. It automatically handles edge cases such as creating a new
> > > frame over ssh in tty mode or being invoked as an emacs subprocess. I
> > > think it would be really useful to upstream a tool like this, given
> > > that using emacs as a merge tool that can be invoked by software such
> > > as mercurial or perforce can be very fiddly or have unexpected
> > > behavior.
> >
> > Can you describe the use of this tool in more detail, and what
> > enhancements it implements beyond what emacsclient provides?  I don't
> > think I understand that from your short description.
> >
> > Thanks.