#!/usr/bin/env bash
#
# git_cleanup.sh
#
# Cleans up local git repository, using origin/master as a
# frame of reference.
#
# * Deletes references to remote branches that have since been removed.
# * Deletes local branches that have been fully merged into master.
# * Garbage collects local git repo.

command -v git >/dev/null 2>&1
if [ "$?" -ne "0" ]; then
  >&2 echo "git not found in PATH"
  exit 1
fi

git rev-parse --git-dir >/dev/null 2>&1
if [ "$?" -ne "0" ]; then
  >&2 echo "not a git directory"
  exit 1
fi

ORIGIN="${ORIGIN:-origin}"
MASTER="${MASTER:-master}"

CURRENT=`git rev-parse --abbrev-ref HEAD 2>/dev/null`

if [ -z "$CURRENT" ]; then
  >&2 echo "unable to get current branch"
  exit 1
fi

if [ "$CURRENT" != "$MASTER" ]; then
  >&2 echo "please checkout $MASTER branch before proceeding"
  exit 1
fi

git pull --ff-only >/dev/null 2>&1
if [ "$?" -ne "0" ]; then
  >&2 echo "failed to fast-forward pull"
  exit 1
fi

# remove local refs to remote branches that no longer exist at the origin
git fetch $ORIGIN -p
if [ "$?" -ne "0" ]; then
  >&2 echo "failed to fetch $ORIGIN"
  exit 1
fi

# delete local branches that have been merged fully into master
git branch --merged $ORIGIN/$MASTER | \
  egrep -v "(^\*|${MASTER})" | \
  xargs -r git branch -d

# garbage collect
git gc >/dev/null 2>&1