place in .git/hooks to get ctags workin

run_tags.rb

#!/usr/bin/env ruby
#-*-ruby-*-
# A script to run ctags on all .rb files in a project. Can be run on
# the current dir, called from a git callback, or install itself as a
# git post-merge and post-commit callback.

require 'rubygems'
require 'ruby-debug'

CTAGS = `which ctags`.chomp
HOOKS = %w{ post-merge post-commit post-rebase post-checkout }
HOOKS_DIR = '.git/hooks'

def install(force)
  if !File.writable?(HOOKS_DIR)
    $stderr.print "The install option [-i] can only be used within a git repo; exiting.\n"
    exit 1
  end

  HOOKS.each { |hook| install_hook("#{HOOKS_DIR}/#{hook}", force) }
end

def run_tags(dir, run_in_background = false)
  if File.executable?(CTAGS) and File.writable?(dir)
    cmd = "find #{dir} -name \\\*.rb | #{CTAGS} -f #{dir}/tags -L - 2>>/dev/null "
    cmd << '&' if run_in_background
    $stderr.puts "Regenerating tags..."
    system cmd
  else
    $stderr.print "FAILED to write TAGS file to #{dir}\n"
  end
end

def install_hook(hook, force)
  if File.exists?(hook) and not force
    $stderr.print "A file already exists at #{hook}, and will NOT be replaced.\n"
    return
  end

  print "Linking #{File.expand_path __FILE__} to #{hook}\n"
  %x{ln -sfF #{File.expand_path __FILE__}  #{hook}}
end

if ARGV.include? '-i'
  force = ARGV.include? "-f"
  install(force)
else
  run_tags Dir.pwd, HOOKS.include?(File.basename(__FILE__))
end