gistfile1.rb

#!/usr/bin/ruby
# rewrite_history.rb
# Jonathan D. Stott <[email protected]>
require 'fileutils'

adapters = %w{
mysql_adapter.rb
postgres_adapter.rb
sqlite3_adapter.rb
oracle_adapter.rb
sqlserver_adapter.rb
abstract_adapter.rb
data_objects_adapter.rb
in_memory_adapter.rb
yaml_adapter.rb
}

def sh(command)
  system command || abort(command)
end

adapters.each do |adapter|
  puts adapter
  name    = adapter.split('_').first
  dirname = "/home/jon/tmp/dm-#{name}-adapter" # this is a ramdrive, for speed.

  # create a clone
  sh "git clone --quiet --no-hardlinks dm-core #{dirname}"

  FileUtils.cd dirname do
    # rewrite to subdir
    sh "git filter-branch --prune-empty --subdirectory-filter lib/dm-core/adapters HEAD -- --all"

    # now, successively rewrite by removing all but our adapter
    to_go = adapters - [adapter]
    to_go.each do |file|
      sh "git filter-branch --force --prune-empty --index-filter 'git rm --cached --ignore-unmatch #{file}' HEAD"
    end

    # clean up after our butchery!
    sh "git reset --hard"
    sh "git prune"
    sh "git gc --aggressive"
    sh "git prune"
    sh "git fsck"
  end

  FileUtils.mv dirname, Dir.pwd
end