Using DiffMerge as your Git visual merge and diff tool on Mac

.gitconfig-for-diffmerge

[diff]
        tool = diffmerge
[difftool "diffmerge"]
        cmd = diffmerge \"$LOCAL\" \"$REMOTE\"
[merge]
        tool = diffmerge
[mergetool "diffmerge"]
        cmd = "diffmerge --merge --result=\"$MERGED\" \"$LOCAL\" \"$(if test -f \"$BASE\"; then echo \"$BASE\"; else echo \"$LOCAL\"; fi)\" \"$REMOTE\""
        trustExitCode = true

git-config.sh

git config --global diff.tool diffmerge
git config --global difftool.diffmerge.cmd 'diffmerge "$LOCAL" "$REMOTE"'
git config --global merge.tool diffmerge
git config --global mergetool.diffmerge.cmd 'diffmerge --merge --result="$MERGED" "$LOCAL" "$(if test -f "$BASE"; then echo "$BASE"; else echo "$LOCAL"; fi)" "$REMOTE"'
git config --global mergetool.diffmerge.trustExitCode true

usr-bin-diffmerge

#!/bin/sh
## A little script to make it easier to launch DiffMerge from the command line.
## Install this script into a folder in your path, such as /usr/bin or /usr/local/bin.
##
## Version 3.3.0.1001
## Copyright (C) 2003-2009 SourceGear LLC. All Rights Reserved.
##############################################################################

## Change DIFFMERGE_PATH to point to where you installed DiffMerge

DIFFMERGE_PATH=/Volumes/App/Applications/DiffMerge.app

## The actual executable is hidden inside the .app bundle.

DIFFMERGE_EXE=${DIFFMERGE_PATH}/Contents/MacOS/DiffMerge

## Launch DiffMerge using the given command line arguments.  Use --help for
## additional information or see the man page distributed along with this
## shell script.

exec ${DIFFMERGE_EXE} --nosplash "$@"