Posting this mostly in case I need it again. I needed a merge tool for Git, Kdiff is free and useful, but you have to get all the switches set up if you want full functionality (three way merge). I found the answer on this blog post (a reminder to us all to share stuff we had to work to find and/or figure out!), copying the code here so I don’t lose it:
[merge]
tool = kdiff3
[mergetool "kdiff3"]
cmd = \"C:\\\\Program Files (x86)\\\\KDiff3\\\\kdiff3\" $BASE $LOCAL $REMOTE -o $MERGED