Git mergertool magic
Explained nicely in http://www.rosipov.com/blog/use-vimdiff-as-git-mergetool/
The default is vimdiff; if you like vim you will like it.
You can just edit the file to manually and hit
:wqas normal once done.
Whoops you merged and you didn’t mean to
git checkout -m <file>
Will return the file to its conflicted state. Can then run git mergetool to redo the merge.