using FileMerge as git difftool on Mac OS X

gdiff

#!/bin/bash
# my git difftool, calls FileMerge with project as -merge target
# better than using opendiff
#
# cd to your project dir and and run difftool like this:
#   git difftool -d -x gdiff

# find top level of git project
dir=$PWD
until [ -e "$dir/.git" ]; do
  if [ "$dir" == "/" ]; then
    echo "Not a git repository" >&2
    exit 1;
  fi
  dir=`dirname "$dir"`
done

# open fresh FileMerge and wait for termination, avoids issues with git temp files
open -a FileMerge -n -W --args -left "$1" -right "$2" -merge "$dir"

# references:
# http://hints.macworld.com/article.php?story=20070220223441729
# https://gist.github.com/bkeating/329690