git-sub-branch

#!/bin/sh

if [ -z "$1" -o -z "$2" ]
then
	echo "Usage:\n\tgit sub-branch <sub-dir> <branch>"
	exit 1;
fi

sumDir="."
tree=`git cat-file commit HEAD | grep '^tree ' | awk '{print \$2}'`

# Find the tree ID for the sub-directory
for dir in `echo "$1" | tr "/" "\n"`
do
	sumDir="$sumDir/$dir"
	if [ ! -z "$dir" ]
	then
		tree=`git cat-file -p "$tree" | grep "\t${dir}$" | awk '{print $3}'`
		if [ -z "$tree" ]
		then
			echo "Could not find sub-dir: ${sumDir}"
			exit 1
		fi
	fi
done

# Copy latest commit message
git log -n 1 --format="%B" > .git/.SUB_BRANCH_MSG

if (git rev-parse --verify "$2" &> /dev/null)
then
	echo "\n\n# adding to branch: $2\n" >> .git/.SUB_BRANCH_MSG
	$EDITOR .git/.SUB_BRANCH_MSG
	commitMsg=`cat .git/.SUB_BRANCH_MSG | sed '/^#/d'`
	newCommit=`cat .git/.SUB_BRANCH_MSG | git commit-tree "${tree}" -p "$2" -m "$commitMsg"`
else
	echo "\n\n# new branch: $2\n" >> .git/.SUB_BRANCH_MSG
	$EDITOR .git/.SUB_BRANCH_MSG
	commitMsg=`cat .git/.SUB_BRANCH_MSG | sed '/^#/d'`
	newCommit=`cat .git/.SUB_BRANCH_MSG | git commit-tree "${tree}" -m "$commitMsg"`
fi
git branch -f "$2" "$newCommit"