Fast-forward merge script for GitHub PRs

merge.sh

#!/usr/bin/env bash

# How to use:
# bash merge.sh <PR-id>

set -e

git checkout master
git pull

branch_name=pr$1

git fetch origin pull/$1/head:$branch_name
git checkout $branch_name

# Check if branch is up-to-date with master.
hash1=$(git show-ref --heads -s master)
hash2=$(git merge-base master $branch_name)
if [ "${hash1}" = "${hash2}" ]; then
    echo "Branch is up-to-date."
else
    echo "Rebase required!"
    exit 1
fi

# Check if all CI checks are green.
curl -s https://api.github.com/repos/coala/${PWD##*/}/commits/$(git rev-parse HEAD)/statuses \
| paste -sd "" - \
| python3 -c 'import json, sys; o = json.loads(input()); c = {x["context"] for x in o}; sys.exit({(x["state"], c.remove(x["context"]))[0] for x in o if x["context"] in c} != {"success"})'

# Merge.
git checkout master
git merge --ff-only $branch_name
git branch -d $branch_name

echo "Merge successful."
echo "Please run 'git push' to update the upstream master branch!"