I have the following in my .gitconfig
file:
[user]
name = myname
email = myname@gmail.com
[core]
autocrlf = true
excludesfile = C:\\
For OS X it looks like this:
Diff Command: /Applications/Meld.app/Contents/MacOS/meld
.
$LOCAL $REMOTE
Merge Command: /Applications/Meld.app/Contents/MacOS/meld
.
$LOCAL $BASE $REMOTE --auto-merge --output=$MERGED
P.S. you might have to configure the order of $local and $ remote in meld prefrences as well..
To use it from command line you have to install it via brew:
brew install meld