git hook to prefix commit messages with ticket number

commit-msg

#!/usr/bin/env ruby
#
# Git commit-msg hook. If your branch name is in the form "#{prefix}-123", automatically
# adds "#{prefix}-123:" to commit messages unless they mention "#{orefix}-123" already.
# Include "#noref" in the message to avoid this behavior for the current commit.
# The "#noref" will be stripped from the commit message.
#
# Modified from script Henrik Nyh <http://henrik.nyh.se> 2009-09-10 under the MIT License.
#
#
# Install:
#
# cd your_project
# curl https://gist.githubusercontent.com/Lacrymology/c72cf9ffc3d9b3692522343de3b3b418/raw/472bf7b52b1346a6fdde5d761cf06ac7cb96f08c/commit-msg -o .git/hooks/commit-msg && chmod u+x .git/hooks/commit-msg
#
# Or store it centrally and symlink in your projects:
#
# curl --create-dirs https://gist.githubusercontent.com/Lacrymology/c72cf9ffc3d9b3692522343de3b3b418/raw/472bf7b52b1346a6fdde5d761cf06ac7cb96f08c/commit-msg -o ~/.githooks/commit-msg && chmod u+x ~/.githooks/commit-msg
# cd your_project
# ln -s ~/.githooks/commit-msg .git/hooks
prefix = 'DAM'
branchname = `git branch --no-color 2> /dev/null`[/^\* (.+)/, 1]
ticket_number = branchname.to_s.match(/\A#{prefix}-(\d+)/) && $1

exit unless ticket_number

message_file = ARGV[0]
message = File.read(message_file)

exit if message.include?("#{prefix}-#{ticket_number}")

message.strip!

if message.include?("#noref")
  message.sub!(/^\s*#noref\s*|\s*#noref/, '')
else
  message.sub!(/([^[:punct:]])\z/, "\\1.")  # Add trailing period if missing.
  message = ["#{prefix}-#{ticket_number}", message,].join(": ")
  puts message
end

File.open(message_file, 'w') {|f| f.write message }