split apart a monolithic repo into several smaller ones while preserving commit history.

splitter.rb

#!/usr/bin/env ruby
BASE_REMOTE_URL = "git@github.blueboxgrid.com:chef"
folders = ARGV
pwd = Dir.pwd
folders.each do |folder|
    name = folder.split("/").last
    name = name.gsub("-","_")
    clone_command = "git clone chef/ #{name}"
    system clone_command
    Dir.chdir name
    filter_command = "git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter #{folder.split("/")[1..-1].join("/")} HEAD"
    system filter_command

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

    `git remote rm origin`

    origin_command = "git remote add origin #{BASE_REMOTE_URL}/#{name}.git"

    system origin_command

    `git push origin master`

    Dir.chdir pwd
end