A git hook which appends a reference to a Pivotal Tracker story ID, if a branch starts with a number (e.g. "<story id>-my-issue")

prepare-commit-msg

#!/bin/sh

# Get the story ID from the branch name
story_id=`git symbolic-ref --short -q HEAD | grep -o "^[[:digit:]]*"`
if [ ! -z "$story_id" -a "$story_id" != " " ]
then
  # If a story ID is found, prepend the commit message with a reference
  echo "[#$story_id] $(cat $1)" > "$1"
fi