Settings for OS X

First confirm that /usr/local/bin/diffmerge is present. If you used the PKG Installer, this was installed when /Applications/ was installed. If you used the DMG file, refer to the instructions for installing the Extras.

The following commands will update your .gitconfig to let GIT use DiffMerge:

$ git config --global diff.tool diffmerge
$ git config --global difftool.diffmerge.cmd
    "/usr/local/bin/diffmerge \"\$LOCAL\" \"\$REMOTE\""

$ git config --global merge.tool diffmerge
$ git config --global mergetool.diffmerge.trustExitCode true
$ git config --global mergetool.diffmerge.cmd 
    "/usr/local/bin/diffmerge --merge --result=\"\$MERGED\"
        \"\$LOCAL\" \"\$BASE\" \"\$REMOTE\""