post-checkout git hook: Run `npm install` if package.json has changed

post-checkout

#!/usr/bin/env ruby

from_commit, to_commit, checkout_type = ARGV

# If type is 0, this is a single-file checkout; abort.
if checkout_type.to_i == 0
  exit 0
end

files_changed = `git diff --name-only #{from_commit} #{to_commit}`

if files_changed.include? 'package.json'
  puts "\npackage.json changed. Running npm install.\n\n"
  exec 'npm install'
end