Setup a git repository master that points at actual repository

externalize.rb

PROJECT_NAME='jsinterop-generator'
PROJECT_SLUG='jsinterop-generator'
UPSTREAM_OWNER='google'
LOCAL_OWNER='realityforge'
LOCAL_BRANCHES_TO_KEEP=%w(TravisCiIntegration)

#WARNING this will delete local branches which may contain your changes
DELETE_LOCAL_BRANCHES=true

def mysystem(command, fail_on_error = true)
  puts "system (#{Dir.pwd}): #{command}" if @verbose
  system(command) || !fail_on_error || (raise "Error executing #{command} in #{Dir.pwd}")
end

mysystem("git clone https://github.com/#{LOCAL_OWNER}/#{PROJECT_SLUG}.git") unless File.exist?(PROJECT_SLUG)

Dir.chdir PROJECT_SLUG

mysystem("git remote add upstream https://github.com/#{UPSTREAM_OWNER}/#{PROJECT_SLUG}.git", false)

mysystem("git fetch upstream")
mysystem("git checkout upstream/master")
mysystem("git branch -f upstream")
mysystem("git checkout upstream")
mysystem("git push --set-upstream -f origin upstream")

if DELETE_LOCAL_BRANCHES
`git ls-remote --heads --refs 2>/dev/null`.split("\n").each do |line|
  if line =~ /^.*refs\/heads\/(.*)$/
    head = $1
    next if (LOCAL_BRANCHES_TO_KEEP + %w(master upstream)).include?(head)
    puts "Removing branch #{head}"    
    mysystem("git push origin :#{head}")
    mysystem("git branch -d #{head}", false)
  end
end
end

`git ls-remote --tags --refs 2>/dev/null`.split("\n").each do |line|
  if line =~ /^.*refs\/tags\/(.*)$/
    tag = $1
    puts "Removing tag #{tag}"    
    mysystem("git push origin :#{tag}")
    mysystem("git tag -d #{tag}")
  end
end

mysystem("git branch -d master", false)
mysystem("git checkout --orphan master")
mysystem("git rm --cached -r .")
mysystem("git add .")
mysystem("git reset --hard")

IO.write("README.md",<<CONTENT)
# Peter Donald's #{PROJECT_NAME} Repository

This repository contains feature branches for the upstream repository: [#{PROJECT_NAME}](https://github.com/#{UPSTREAM_OWNER}/#{PROJECT_SLUG}).
It doesn not contain a meaningful master branch.
CONTENT

mysystem("git add -f README.md")
mysystem('git commit -m "Add a README that describes the purpose of the repository."')
mysystem("git push --set-upstream -f origin master")
mysystem("git checkout upstream")