git-split: Break off a sub directory into its own repo, keeping history.

gistfile1.rb

#! /usr/bin/env ruby

require 'tmpdir'
require 'fileutils'
require 'pp'

def main()

  directory = ARGV.shift

  unless File.exists?(directory)
    puts "directory #{directory} does not exist"
    exit 1
  end

  dirname=%x{basename #{directory}}.chomp
  git_dir=%x{git rev-parse --show-toplevel}.chomp
  branch=%x{git symbolic-ref --short -q HEAD}.chomp

  Dir.mktmpdir(nil, '/var/tmp') {|dir|
    dst = "#{dir}/#{dirname}"
    FileUtils.mkdir_p(dst)
    #FileUtils.copy_entry(git_dir,dst)
    %x{git clone #{git_dir} #{dst}}
    FileUtils.cd(dst)
    puts "working in #{dst}"

    remotes=[%x{git remote}.split("\n").map{|r| r.chomp}].flatten.reject{|r| r.empty? }

    # Remove all remotes
    remotes.each {|r|
      %x{git remote remove #{r}}
      %x{git remote set-head -d #{r}}
    }

    # rename the branch
    if branch != 'master'
      %x{git br -m #{branch} master}
    end

    %x{git filter-branch -f --tag-name-filter cat --prune-empty --subdirectory-filter #{directory}}
    #%x{git filter-branch -f --subdirectory-filter #{directory}}
    #%x{git filter-branch -f --subdirectory-filter #{directory}}

    %x{git reset --hard}
    %x{git for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git update-ref -d}
    %x{git reflog expire --expire=now --all}
    %x{git gc --aggressive --prune=now}

    FileUtils.cd(dir)
    finaldir = "#{git_dir}/#{directory}.split"
    begin
      FileUtils.mv(dirname,finaldir)
    rescue Errno::EEXIST
      puts "Final directory #{finaldir} already exists, aborting!"
      exit 1
    end
  }
end

main()