Diffing files you've got open in your Emacs
M-x ediff-buffers
Diffing revisions of a file
C-x v = (vc-diff)
You can also view the changes with ediff using M-x
ediff-revision
Inside an ediff session
Once inside an ediff session, put focus in the ediff navigator and
use e.g.:
- n/p - next/previous hunk
- a - apply version A's hunk
- b - apply version B's hunk
- r - revert, undo the applying of the A/B hunk.
- q - quit ediff session
Resolving merge conflicts in files with merge conflict markers
Out of the box Emacs gives us an easy interface to working with merge
conflicts, called smerge (as in "simple merge").
When there's a merge conflict, the version control system writes the diff markers into the source files themselves and Emacs will highlight these automatically. It will recognise which parts are "theirs" and which are "mine" — as well as "ancestor" if you've set up 3 way merge.
To select the version at the bottom, I just put my pointer on it, and
run M-x smerge-keep-current.
Telling Git to give us 3 way diff instead of two way
By default git sets up 2 way diffs when there's a merge conflict ("my" version of the file and "their" version). However, when resolving merge conflicts, it's often useful to in addition see the most recent common ancestor of the two versions of the file you're merging.
This is so useful, you may just want to set it globally for all your
projects by adding the following to your ~/.gitconfig:
[merge]
conflictstyle = diff3
*)
Tested on version Emacs version 25.1
P4 specific setup
in .p4enviro:
P4MERGE=/home/torstein/bin/p4-emacs-merge
in .emacs:
(server-start)
in /home/torstein/bin/emerge (Gentoo users, note the full path ;-)
ancestor=$1
theirs=$2
yours=$3
merge_result=$4
emacsclient -e "(ediff-merge-files-with-ancestor \"${yours}\" \"${theirs}\" \"${ancestor}\" () \"${merge_result}\")"
emacsclient "${merge_result}"
The full source of p4-emacs-merge can be found here: https://github.com/skybert/my-little-friends/blob/master/bash/vcs/p4-emacs-merge
P4 specifc post-merge notes
After you're finished with the ediff session and you're back at the
p4/shell prompt, choose ae (accept edit) Here's one merge
conflict, with the two version presented (p4 "yours" is A and p4
"theirs" is B):
Now, I want "their" version, so I hit b. Emacs then replaces the merge conflict markers/block with the contents of the B hunk:
