Script for backporting OpenStack branches

bp.sh

#!/usr/bin/env bash
# This is a little script to make backporting patches.
# Instructions
# ------------
# Make sure that milestone-proposed exists and is up to date:
#   git branch -D milestone-proposed
#   git checkout -b milestone-proposed origin/<branch>
#   git pull
# Grab the file and stick it in your <project> directory:
#   curl -OL https://raw.github.com/gist/2206428/bp.sh
# Make sure the script is runnable:
#   chmod 755 bp.sh
# Start backporting reviews:
#   ./bp.sh <review_number>
# Recovering from errors
# ----------------------
# If you have previously downloaded a branch you will see a failure
# from git-review -d that branch xxxx/xxxx/xxxx already exists
# to recover you will need to delete two branches:
#   git branch -D xxxx/xxxx/xxxx
#   git branch -D bp-<review_number>
# If your branch fails to merge cleanly it is usually due to
# a dependent branch not being in yet.  In that case your best bet
# is to wait for the dependent branch to merge, then:
#   git checkout <branch>
#   git pull
#   git branch -D xxxx/xxxx/xxxx
#   git branch -D bp-<review_number>
# and rerun the script

if [ -z "$1" ]; then
    echo "Usage: $0 <review_number> [<branch=milestone-proposed>]"
    exit 1
fi

$BRANCH=${1-milestone-proposed}

git review -d $1
git checkout $BRANCH
git checkout -b bp-$1
git cherry-pick -x HEAD@{2}
git review $BRANCH
REMOTE=`git remote show gerrit -n | grep Fetch | cut -d'/' -f3`
PORT=`echo $REMOTE | cut -d':' -f2`
HOST=`echo $REMOTE | cut -d':' -f1`
SHA=`git rev-parse HEAD`
echo "Use the following line to approve the review"
echo "ssh -p $PORT $HOST gerrit review --code-review +2 --approved +1 $SHA"