git-commit-as

#!/usr/bin/env ruby
# usage: git-commit-as github-username -m 'commit message'

require 'open-uri'
require 'rexml/document'

def main
  username = ARGV.shift
  userid = userid(username)

  system('git', 'commit', *ARGV)
  system(<<COMMAND)
git filter-branch -f --commit-filter '
  GIT_AUTHOR_NAME="#{username}"
  GIT_AUTHOR_EMAIL="#{userid}"
  GIT_COMMITTER_NAME="#{username}"
  GIT_COMMITTER_EMAIL="#{userid}"
  git commit-tree "$@"
' HEAD^..HEAD
COMMAND
end

def userid(username)
  doc = REXML::Document.new(open('http://github.com/api/v2/xml/user/show/' + username).read)
  doc.elements['/user/id'].get_text 
end

main