emerge-files from command line fails (merging out of unison)

[Karl Voit <devnull@Karl-Voit.at>]

Hi!

I am using unison file syncronizer to sync my notebook with my
desktop. This tool uses a special syntax[1] to call an external tool
to do the merging-job. I want to use my emacs with emerge to merge
files.

Fortunately, I found [2] to help me in this case. But when I merge
files (file-A and file-B are opened correctly) and quit the
merge-process ('q'), unison complains, that emacs didn't generate an
outfile which is indeed the case (no such filename exists).

And I cannot figure out, how emacs should know about the name of the
outfile, when I take a look at the proposed[2] code-sniplet:

1:(defun mlw-emerge-files-command ()
2:  (let ((file-a (nth 0 command-line-args-left))
3:        (file-b (nth 1 command-line-args-left)))
4:    (setq command-line-args-left (nthcdr 2 command-line-args-left))
5:    (emerge-files-internal
6:     file-a file-b nil nil nil)))

In line 6, there are file-a and file-b entered as parameters for
emerge-files-internal but I guess, there should be something like
file-new too.

So I tried to modify the code: (without really knowing emacs-LISP at all!)

1:(defun vk-emerge-files-command ()
2:  (let ((file-a (nth 0 command-line-args-left))
3:        (file-b (nth 1 command-line-args-left))
4:        (file-new (nth 2 command-line-args-left)))
5:    (setq command-line-args-left (nthcdr 3 command-line-args-left))
6:    (emerge-files-internal
7:     file-a file-b nil nil file-new)))

But this does not generate the correct result-file too :-(

I think it should be that way, that the file-new (in this case
"$HOME/.unison/#unisonmerged-file") should appear _instead_ of the
*merge*-buffer, right? But there is no such buffer. But
emerge-files-internal should expect the outfile as last parameter, right?


Unison calls my emerge-Script which contains basically following line
   emacs --eval "(vk-emerge-files-command)" $@
to merge files. The parameters in $@ are file-a, file-b and file-new (I
already verified, that this reaches the emacs-call correctly).

What do I do wrong?

[1] http://www.cis.upenn.edu/~bcpierce/unison/manual.html#merge

[2] http://mail.gnu.org/archive/html/help-gnu-emacs/2003-01/msg00805.html

-- 
Karl VOIT, Graz University of Technology (Austria/Europe)