How to use pure Vim as git mergetool?

Question

Whenever there are some git merge conflicts we would type git mergetool and git would automatically launch a merge tool for us to merge the conflicts. I have been using vimdiff for a long time as my mergetool, but found it actually not efficient at all as using three-way merging won't provide more information but would occupy the precious screen space.

So I am really interested in using pure vim (not in diff mode) as my git mergetool. But I can't configure it directly since git only accepts certain difftools as git mergetool(opendiff kdiff3 tkdiff xxdiff meld tortoisemerge gvimdiff diffuse diffmerge ecmerge p4merge araxis bc codecompare emerge vimdiff).

So I am wondering if there is way that I can configure pure vim as my tool to solve conflicts? Note using vim to open and edit the conflicted files directly is not desired here since you would lose a lot of conveniences provided by calling git mergetool, including automatic file opening and automatic git staging.

Answer 1

I think something like this in your ~/.gitconfig file should do what your asking.

[merge] 
    tool = myvimdiff
[mergetool "myvimdiff"]
    cmd = vim "$MERGED"

There are lots of other options for the mergetool besides cmd, search for merge.<tool>. in man git-config (and obviously you can customise cmd how you like it. When merging 4 files are available: $LOCAL, $BASE, $REMOTE, and $MERGED (again look at the documentation for that). You can see how git sets up the default tools here if you want more inspiration.