Using ediff as git mergetool

I use a a more complicated command. As far as I remember I got it from this thread http://kerneltrap.org/mailarchive/git/2007/6/28/250230 (probably the same as what you are referring to).

[mergetool.ediff]    cmd = emacs --eval \"\(progn\  (defun ediff-write-merge-buffer ()\    (let ((file ediff-merge-store-file))\      (set-buffer ediff-buffer-C)\      (write-region (point-min) (point-max) file)\      (message \\\"Merge buffer saved in: %s\\\" file)\      (set-buffer-modified-p nil)\      (sit-for 1)))\  (setq ediff-quit-hook 'kill-emacs\        ediff-quit-merge-hook 'ediff-write-merge-buffer)\  (ediff-merge-files-with-ancestor \\\"$LOCAL\\\" \\\"$REMOTE\\\"\                                   \\\"$BASE\\\" nil \\\"$MERGED\\\"))\"

Note that I have split this across several lines to increase readability and escaped the newline with \ so git config considers it as a single line.

I usually use emacsclient to edit e.g. commit messages. The above mergetool configuration unfortunately does not use emacsclient, and when I tried to get it to work with emacsclient I ran in to various problems including the fact that emacsclient returned right away.

But you just reminded me of that issue, so I might work on fixing that problem soon. However if someone else already found a solution that would be great of course ;-)

I use the following script as mergetool which works quite well.

#!/bin/bash# test argsif [ ! ${#} -ge 3 ]; then    echo 1>&2 "Usage: ${0} LOCAL REMOTE MERGED BASE"    echo 1>&2 "       (LOCAL, REMOTE, MERGED, BASE can be provided by \`git mergetool'.)"    exit 1fi# tools_EMACSCLIENT=/usr/local/bin/emacsclient_BASENAME=/bin/basename_CP=/bin/cp_EGREP=/bin/egrep_MKTEMP=/bin/mktemp# args_LOCAL=${1}_REMOTE=${2}_MERGED=${3}if [ -r ${4} ] ; then    _BASE=${4}    _EDIFF=ediff-merge-files-with-ancestor    _EVAL="${_EDIFF} \"${_LOCAL}\" \"${_REMOTE}\" \"${_BASE}\" nil \"${_MERGED}\""else    _EDIFF=ediff-merge-files    _EVAL="${_EDIFF} \"${_LOCAL}\" \"${_REMOTE}\" nil \"${_MERGED}\""fi# console vs. Xif [ "${TERM}" = "linux" ]; then    unset DISPLAY    _EMACSCLIENTOPTS="-t"else    _EMACSCLIENTOPTS="-c"fi# run emacsclient${_EMACSCLIENT} ${_EMACSCLIENTOPTS} -a "" -e "(${_EVAL})" 2>&1# check modified fileif [ ! $(egrep -c '^(<<<<<<<|=======|>>>>>>>|####### Ancestor)' ${_MERGED}) = 0 ]; then    _MERGEDSAVE=$(${_MKTEMP} --tmpdir `${_BASENAME} ${_MERGED}`.XXXXXXXXXX)    ${_CP} ${_MERGED} ${_MERGEDSAVE}    echo 1>&2 "Oops! Conflict markers detected in $_MERGED."    echo 1>&2 "Saved your changes to ${_MERGEDSAVE}"    echo 1>&2 "Exiting with code 1."    exit 1fiexit 0

To use it with `git mergetool' put the following in your git config:

[merge]        tool = ediff[mergetool "ediff"]        cmd = /path/to/ediff-merge-script $LOCAL $REMOTE $MERGED $BASE        trustExitCode = true

Additionally, you should check (in the script) the paths of the tools used and if the poor man's console detection works for you.

The script itself starts an emacs client (or emacs followed by an emacs client, -a "") and evals either ediff-merge-files-with-ancestor or ediff-merge-files if there's no base version (e.g. when merging two branches where the same path/file has been created independently).

After the emacs client has finished the merged file is checked for conflict markers. Should those be found, your work will be saved away to a temporary file, the script will exit with code 1 and git will restore the pre-mergetool contents of the merged file.

When there are no conflict markers present, the script exits with code 0 and git will regard the merge as successful.

Important: Setting the mergetool option trustExitCode to true as well as the post-edit check for conflict markers will not work if you start emacsclient with the --no-wait option.

Here's my setup, which works fairly well, using Emacs 23.3 at least. The trick I used was using (recursive-edit) in a hook such that emacsclient does not exit until an advised ediff-quit hook calls (exit-recursive-edit).

I used an advisted ediff-quit to ensure the exit-recursive-edit is the very last thing done.

There are also hooks to save the current frame and window state and restore it afterwards, and the hook makes the current frame fill the screen. You may wish to modify that, but I find merging full screen is the best way.

I've not solved the issue of aborting the ediff and making emacsclient return a non-zero exit.

Put in your gitconfig:

[mergetool "ediff"]       cmd = emacsclient --eval \"(git-mergetool-emacsclient-ediff \\\"$LOCAL\\\" \\\"$REMOTE\\\" \\\"$BASE\\\" \\\"$MERGED\\\")\"       trustExitCode = true[mergetool]    prompt = false[merge]    tool = ediff

Put in your .emacs or equivalent:

;;;; Setup for ediff.;;(require 'ediff)(defvar ediff-after-quit-hooks nil  "* Hooks to run after ediff or emerge is quit.")(defadvice ediff-quit (after edit-after-quit-hooks activate)  (run-hooks 'ediff-after-quit-hooks))(setq git-mergetool-emacsclient-ediff-active nil)(defun local-ediff-frame-maximize ()  (let* ((bounds (display-usable-bounds))     (x (nth 0 bounds))     (y (nth 1 bounds))     (width (/ (nth 2 bounds) (frame-char-width)))     (height (/ (nth 3 bounds) (frame-char-height))))    (set-frame-width (selected-frame) width)    (set-frame-height (selected-frame) height)    (set-frame-position (selected-frame) x y)))(setq ediff-window-setup-function 'ediff-setup-windows-plain)(setq ediff-split-window-function 'split-window-horizontally)(defun local-ediff-before-setup-hook ()  (setq local-ediff-saved-frame-configuration (current-frame-configuration))  (setq local-ediff-saved-window-configuration (current-window-configuration))  (local-ediff-frame-maximize)  (if git-mergetool-emacsclient-ediff-active      (raise-frame)))(defun local-ediff-quit-hook ()  (set-frame-configuration local-ediff-saved-frame-configuration)  (set-window-configuration local-ediff-saved-window-configuration))(defun local-ediff-suspend-hook ()  (set-frame-configuration local-ediff-saved-frame-configuration)  (set-window-configuration local-ediff-saved-window-configuration))(add-hook 'ediff-before-setup-hook 'local-ediff-before-setup-hook)(add-hook 'ediff-quit-hook 'local-ediff-quit-hook 'append)(add-hook 'ediff-suspend-hook 'local-ediff-suspend-hook 'append);; Useful for ediff merge from emacsclient.(defun git-mergetool-emacsclient-ediff (local remote base merged)  (setq git-mergetool-emacsclient-ediff-active t)  (if (file-readable-p base)      (ediff-merge-files-with-ancestor local remote base nil merged)    (ediff-merge-files local remote nil merged))  (recursive-edit))(defun git-mergetool-emacsclient-ediff-after-quit-hook ()  (exit-recursive-edit))(add-hook 'ediff-after-quit-hooks 'git-mergetool-emacsclient-ediff-after-quit-hook 'append)