Splitting a repo (on git versions 1.7.11+, this is done with git subtree)

split_repo.sh

#/bin/bash

git clone unicorn unicorn-calendar
cd unicorn-calendar
git filter-branch --prune-empty --subdirectory-filter apps/calendar master
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
git remote rm origin

# Add a new origin