bug#25547: 25.1.91; emacsclient -c creates frames on the wrong display

[Stefan Monnier <monnier@iro.umontreal.ca>]

> It looks like I was able to make progress today. Just by modifying
> server.el, I've gotten `emacsclient -ce "..."` to create a new frame
> based on the currently selected frame's terminal when called in a dumb
> terminal.

Great!

> Unfortunately, the command for calling ediff is still very
> unpleasant:
>
> 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 the problem is that emacsclient lacks the equivalent of `-f`,
i.e. calling a particular ELisp function where the remaining arguments
can be consumed by that function.  That would solve the problem of
quoting (your above script will stumble when encountering
a file name with quotes in it or with a final backslash).

> So perhaps introducing a wrapper script for ediff merges would still be useful.

We should be able to add a convenience `batch-ediff-merge-with-ancestor`.
Bonus points if you manage to make it work with `emacs --batch -f` as
well as with `emacsclient --<newflag>`.


        Stefan