Extract a git directory as a separated project

git-tear.sh

#!/bin/bash
SUBDIR=$1

if [ "$SUBDIR" = "" ]; then
  echo "You have to enter a subdir as first arg"
  exit -1
fi

if [ ! -e $SUBDIR ]; then
  echo "$SUBDIR must exist. Are you in the repo root?"
  exit -1
fi

echo "Removing old origin"
git remote rm origin

echo "Filtering only the requested subdir ($SUBDIR)"
git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter $SUBDIR HEAD

echo "Purges repo of all unrelated references"
git reset --hard
git for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git update-ref -d
git reflog expire --expire=now --all
git gc --aggressive --prune=now

echo "All done."