split off subdirectories of a git repo to their own repo.

splitter.rb

#!/usr/bin/env ruby

# preliminary:
#
# git clone remote_repo repo
# cd repo
# for remote in `git branch -r | grep -v master `; do git checkout --track $remote ; done

def git_repo(subdir)
  if File.directory?(subdir + "/.git")
    File.absolute_path(subdir)
  else
    git_repo(subdir + "/..")
  end
end

def subdirectory(origin, subdir)
  o = File.absolute_path(origin).split("/")
  s = File.absolute_path(subdir).split("/")
  while o.first == s.first
    o.shift
    s.shift
  end
  s.join('/') + '/'
end

def track_all_branches!
  system 'for remote in `git branch -r | grep -v master `; do git checkout --track $remote ; done'
  system 'git checkout master'
end

# remove merged branches 
# the current directory needs to be a git repo
def remove_merged_branches!
  `git checkout master`
  `git branch --merged`.each_line do |merged_branch|
    next if merged_branch.include?("*") # * designates the branch we're on
    puts "\tdeleting merged branch '#{merged_branch.strip}'..."
    `git branch -d #{merged_branch.strip}`
  end
end

folders = ARGV
pwd = Dir.pwd
folders.each do |folder|
  repo = git_repo(folder)

  name = folder.split("/").last
  name = name.gsub("-","_")
  puts "-" * 80, "Cloning #{folder}, #{name}..."
  clone_command =  "git clone #{repo} #{name}"
  puts clone_command
  system clone_command
  
  subdir = subdirectory(repo, folder)
  puts "-" * 80, "Filtering... #{subdir}"
  Dir.chdir name
  filter_command = "git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter #{subdir} -- --all"
  # system filter_command

  `#{filter_command} 2>&1`.each_line do |line|
    # for all branches that look like
    #   WARNING: Ref 'refs/remotes/origin/photo_bouncing' is unchanged
    # we should delete that branch.
    puts "\n"
    if line =~ /Ref \'refs\/remotes\/origin\/([\w\_\-]+)\' was rewritten/
      puts "Keeping '#{$1}':\t(#{line.strip})"
      system "git checkout #{$1}"
    else
      puts "Ignoring (#{line.strip})"
    end
  end

  puts "-" * 80, "Cleaning..."
  remove_merged_branches!
  `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`

  puts "Done."
  Dir.chdir pwd
end