git commit-msg hook to prepend commit messages with a JIRA ticket number

commig-msg.rb

#!/usr/bin/env ruby
#
# Jon Sibley, Sept 17 2013, based on this gist: https://gist.github.com/hakanensari/4194831
#
# A minimal commit message hook that extracts a JIRA ticket number from the branch
# name and appends it to the commit message.
#
# The commit message remains unchanged if the branch name doesn't include a
# ticket number or the message already includes a reference to it.
#
# Let's assume you have a story that outlines that you want to deliver foo
# value. You start by checking out a branch:
#
#    123-deliver-foo-feature
#
# You commit a unit of work:
#
#    Did bar
#
# This becomes:
#
#    IOS-123 Did bar
#

branchname = `git name-rev --name-only HEAD 2>/dev/null`.strip
 
exit unless branchname.match(/^(\d+)/)
ticket = "#{$1}"
 
message_file = ARGV[0]
message = File.read(message_file)

# exit if message.include? "IOS-" + ticket 

prepended_message = "IOS-#{ticket} " + message
 
File.open(message_file, 'w') { |f| f.write prepended_message }