Emacs Diff at Point

This is a utility for navigating between changes in your repository, by opening a diff, and by navigating to the lines inside it.

Available via melpa.

See demo video.

Motivation

When working on a task that touches multiple files, it's often useful to navigate between these changes.

Features

diff-at-point-open-and-goto-hunk

Creates a diff for the current repository, navigating to the current point (where possible).

diff-at-point-goto-source-and-close

Go to the location at the point, closing the current diff buffer.

Usage

You may bind the functions to keys, in specific modes.

This is not a minor mode, instead, there are two main functions you can bind yourself:

Here are example bindings which use Ctrl-Alt-Return.

(add-hook 'diff-mode-hook
  (lambda ()
    (define-key diff-mode-shared-map (kbd "<C-M-return>") 'diff-at-point-goto-source-and-close)))

(add-hook 'prog-mode-hook
  (lambda ()
    (define-key prog-mode-map (kbd "<C-M-return>") 'diff-at-point-open-and-goto-hunk)))

Or you can use a global binding which checks the major mode.

(global-set-key (kbd "<C-M-return>")
  (lambda () (interactive)
    (cond
      ((string= major-mode "diff-mode")
        (diff-at-point-goto-source-and-close))
      (t
        (diff-at-point-open-and-goto-hunk)))))

Customization

diff-at-point-diff-command

This is the function used to create the diff buffer.

While there is no need to change this value from it's default (calling vc-root-diff) it can be overridden for different behavior.

This example shows how Emacs 27's vc-root-version-diff can be used to diff the working copy against a branch instead of HEAD of a git repository.

(define-key prog-mode-map (kbd "<C-M-return>")
  '(lambda ()
     (interactive)
     (let ((diff-at-point-diff-command
           '(lambda () (vc-root-version-diff nil "main" nil))))
       (diff-at-point-open-and-goto-hunk))))