git-this.rb

#!/usr/bin/env ruby
class File
  def self.svn? path
    File.exists?(path + '/.svn/')
  end
  def self.git? path
    File.exists?(path + '/.git/')
  end
  def self.hg? path
    File.exists?(path + '/.hg/')
  end
end

def git_init!(path)
  puts 'Not a Subversion or Git repo already.'
  puts 'Gitting...'
  command = %`cd '#{path}'; git init; git add ./; git ci -m 'First Commit'`
  puts command
  system command unless TESTING
  puts
end

def convert_svn_to_git!(path)
  puts "Is a Subversion repo."
  # abort if dirty
  abort "Working copy is dirty. Clean up and try again :P \n   or use the --force" unless `cd '#{path}'; svn st`.chomp.empty? unless FORCE
  
  puts "Converting to git..."
  
  # Get subversion info
  svn_info = `cd '#{path}'; svn info`
  
  # Parse out the url
  svn_url = svn_info.scan(/URL: (.*?)\n/).first.first
  require 'cgi'
  svn_url = CGI.unescape svn_url
  git_path = $path + '.gitting'
  svn_path = $path + '.svn'
  
  abort "#{git_path} exists!" if File.exists? git_path
  abort "#{svn_path} exists!" if File.exists? svn_path
  
  command = %`\ngit-svn clone '#{svn_url}' \\\n   '#{git_path}'\n`
  puts command;system command unless TESTING
  
  # Swap the out with the new
  command = %`mv '#$path' \\\n   '#{svn_path}'`
  puts command;system command unless TESTING
  
  command = %`mv '#{git_path}' \\\n   '#$path'`
  puts command;system command unless TESTING
  
  command = %`cd '#$path'`
  puts command;system command unless TESTING
  
  # Get rid of the original
  puts "\n# You'll need to manually remove the original Subversion folder\n    rm -rf '#{svn_path}'"
end

TESTING = true

# Setup
$path = File.expand_path(ARGV[0] || ENV['PWD'])
$path = ENV['PWD'] if ARGV[0] == '--force'
FORCE = ARGV[0] == '--force'

# Help
abort %`Bad path :(\nUsage: #{File.basename __FILE__} [PATH] [--force]` unless File.exists? $path

# Fail if this is already a git repo
abort 'Alteady a git repo :-/' if File.git? $path

# If an hg repo
abort "Doesn't support Mercruial yet :'(" if File.hg? $path

# If this isn't a subversion repo...
if File.svn? $path
  # then just git init.
  git_init! $path unless File.svn? $path
else
  # Otherwise, convert!
  convert_svn_to_git! $path
end
puts