Bash script for working with git subtree merge

subtree_merge.sh

#! /bin/bash
# Based off of http://www.kernel.org/pub/software/scm/git/docs/howto/using-merge-subtree.html

if [[ ! "$2" || ("$3" && ! "$4" ) ]]
then
	filename=`echo "$0"| sed "s/.*\///"`
	echo "Usage: $filename remote_name repo_url branch_name path_to_merge_to"
	echo "        * Create a new subtree merge"
	echo "       $filename remote_name branch_name"
	echo "        * Pull from remote_name/branch_name into subtree"
	exit 0
fi

if [ "$3" ]
then # Create our subtree
	echo "Creating new subtree merge"
	name=$1
	url=$2
	branch=$3
	path=$4

	git remote add -f $name $url
	git merge -s ours --no-commit $name/$branch
	git read-tree --prefix=$path -u $name/$branch
	git commit -m "Subtree-merge $url branch '$branch' to $path"

else # Pull!
	echo "Performing subtree pull"
	name=$1
	branch=$2
	git pull -s subtree $name $branch
fi