Running multiple instances of yarnpkg jobs on CI servers

darn.sh

#!/bin/bash

# Place this file in your /usr/local/bin and then use darn instead of calling yarn
# This will wrap all your yarn calls to go through the same network mutex
# Calling yarn as before still works too if needed.

# --- Motivation ---
# Running multiple build jobs on CI servers like Jenkins will cause contention of
# shared yarnpkg resources (cache). This is going to end up badly for builds going
# out for deployment. This problem is usually not seen locally because devs rarely build
# multiple projects at a time on their local machines.

set -ex
yarn "$@" --mutex network