Using ediff as git mergetool

user_205756 0
Viewed 28908

I would like to be able to use ediff with "git mergetool".

I found some patches that alter the source code, which I don't want to do. Instead, I'd like to add ediff support with my .gitconfig.

I know git has builtin support for emerge, but I prefer ediff.

I attempted to add these lines to my .gitconfig:

[mergetool "ediff"]
    cmd = emacs --eval "(ediff-merge-files-with-ancestor \"$LOCAL\" \"$REMOTE\" \"$BASE\" nil \"$MERGED\")"

But when I try to run this with "git mergetool --tool=ediff", I get this:

eval: 1: Syntax error: "(" unexpected

What am I doing wrong?

merge emacs git
12 Answers

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)
user_5515280

The elisp code in Viper3369's code (Using ediff as git mergetool) uses a function "display-usable-bounds" which doesn't exist. Since the hooks do a lot more than is strictly necessary, simply deleting all references to "display-usable-bounds" is sufficient to make it work for me. Good work! ;)

(Edit: I think I should post the modified emacs-lisp code:

;;
;; 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)


(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)
user_5652240
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