update-mathjax-component

#!/usr/bin/env ruby
# This script clones the MathJax and MathJax-grunt-cleaner repos,
# and runs the `grunt component` command to take all the tags on the main repo
# and make new tags on the components repo with the image fonts removed.
# Pre-existing tags will not be updated.

$cleaner_repo = 'https://github.com/mathjax/MathJax-grunt-cleaner'
$mathjax_repo = 'https://github.com/mathjax/MathJax'
$component_repo = 'git@github.com:components/MathJax'


def run(cmd)
  # echo and run a command, exit on failure
  puts "> #{cmd}"
  if not system(cmd)
    STDERR.write("#{cmd} failed")
    Process.exit(1)
  end
end

def clone_repos(mj_path, cleaner_path)
  # Clone various repos (cleaner, mathjax, and add components remote to mathjax)
  
  cleaner_path = File.absolute_path(cleaner_path)
  mj_path = File.absolute_path(mj_path)
  
  if not File.exists? cleaner_path
    run "git clone #{$cleaner_repo} #{cleaner_path}"
    Dir.chdir cleaner_path do
      run "npm install"
    end
  end
  
  if not File.exists? mj_path
    run "git clone #{$component_repo} -o component #{mj_path}"
  end

  Dir.chdir mj_path do
    run "git fetch component"

    remotes = `git remote`.split
    if not remotes.include? 'upstream'
      run "git remote add upstream #{$mathjax_repo}"
    end
    run "git fetch upstream"
  end

  [mj_path, cleaner_path]
end

def link_files(mj_path, cleaner_path)
  # link build files 
  ['Gruntfile.js', 'node_modules', 'package.json'].each do |f|
    mj_file = File.join(mj_path, f)
    cleaner_file = File.join(cleaner_path, f)
    if not File.exists? mj_file
      puts "Symlinking #{mj_file} → #{cleaner_file}"
      File.symlink(cleaner_file, mj_file)
    end
  end
end

def get_tags(remote)
  # get tags from a particular remote
  tags = {}
  `git ls-remote --tags #{remote}`.split("\n").each do |line|
    sha, ref = line.split
    if ref.include? '^' or ref.include? '-'
      next
    end
    tag = ref.slice('refs/tags/'.length, ref.length)
    tags[tag] = sha
  end
  tags
end


def clear_tags
  # Clear the local tags
  tags = `git tag`.strip.gsub("\n", " ")
  if not tags.empty?
    run "git tag -d #{tags}"
  end
end


def make_component_tag(tag, sha, mj_path, cleaner_path)
  # make a component tag from an upstream tag
  puts "Making component tag #{tag}"
  run "git reset --hard"
  run "git checkout #{sha}"
  link_files(mj_path, cleaner_path)
  run "grunt component"
  run "git add unpacked fonts"
  run "git commit -m 'strip png-fonts for component release #{tag}'"
  run "git tag -f -am 'component tag #{tag}' #{tag}"
end


def migrate_tags(mj_path, cleaner_path)
  # migrate tags from upstream to component repo
  # running Grunt task to strip png image fonts on each
  upstream_tags = get_tags "upstream"
  component_tags = get_tags "component"

  # filter out existing tags on component repo
  component_tags.keys.each do |tag|
    upstream_tags.delete(tag)
  end

  if upstream_tags.empty?
    puts "All tags up-to-date"
    return
  end

  to_push = []
  upstream_tags.each_pair do |tag, sha|
    make_component_tag(tag, sha, mj_path, cleaner_path)
    to_push.push(tag)
  end

  run "git push component " + to_push.join(" ")
end


# actually do it:
mj, cleaner = clone_repos('mathjax', 'mathjax-cleaner')
Dir.chdir mj do
  migrate_tags(mj, cleaner)
end