merge_git_repos.rb

#!/usr/bin/env ruby
#
# Merge multiple git repositories into a new one.
# Users `git filter-branch` to rewrite paths, so that `git log` works seamlessly
# Built from the script at http://dominik.honnef.co/posts/2016/04/merging-git-repositories/
#------------------------------------------------------------------------------

new_repo    = '/tmp/new_repo'
base        = 'git@github.com:customer'
dest_branch = 'master'
projects    = [
  {repo: 'project_one', new_directory: 'one', branch: 'stable'},
  {repo: 'project_two', new_directory: 'two', branch: 'stable'}
]

`mkdir -p "#{new_repo}"`
Dir.chdir(new_repo) do
  puts "--> creating new repository at #{new_repo} and switching to branch '#{dest_branch}'"
  `git init`
  `git commit --allow-empty -m "Initial commit"`
  if dest_branch != 'master'
    `git checkout -b #{dest_branch}`
  end
  projects.each do |prj|
    puts "\n--> Fetching '#{base}/#{prj[:repo]}' into '#{prj[:new_directory]}'"
    `git remote add "#{prj[:new_directory]}" "#{base}/#{prj[:repo]}"`
    system("git fetch '#{prj[:new_directory]}'")

    puts "\n--> Rewriting history to reference '#{prj[:new_directory]}'"
    system("git filter-branch -f --index-filter \
      'git ls-files -s | sed \"s%\\\t\\\"*%&'\"#{prj[:new_directory]}\"'/%\" | \
        GIT_INDEX_FILE=$GIT_INDEX_FILE.new git update-index --index-info && \
            mv \"$GIT_INDEX_FILE.new\" \"$GIT_INDEX_FILE\"' \"#{prj[:new_directory]}/#{prj[:branch]}\"")

    system("git merge -m 'Merge #{prj[:repo]}' '#{prj[:new_directory]}/#{prj[:branch]}'")
    `git remote rm "#{prj[:new_directory]}"`
    puts "\n--> Merged branch '#{prj[:branch]}' into destination branch '#{dest_branch}'"
  end
end