brew/Library/Homebrew/dev-cmd/update-test.rb

#:  * `update-test` [`--commit=`<commit>] [`--before=`<date>] [`--to-tag`] [`--keep-tmp`]:
#:    Runs a test of `brew update` with a new repository clone.
#:
#:    If no arguments are passed, use `origin/master` as the start commit.
#:
#:    If `--commit=`<commit> is passed, use <commit> as the start commit.
#:
#:    If `--before=`<date> is passed, use the commit at <date> as the
#:    start commit.
#:
#:    If `--to-tag` is passed, set `HOMEBREW_UPDATE_TO_TAG` to test updating
#:    between tags.
#:
#:    If `--keep-tmp` is passed, retain the temporary directory containing
#:    the new repository clone.

require "cli_parser"

module Homebrew
  module_function

  def update_test
    Homebrew::CLI::Parser.parse do
      switch "--to-tag"
      switch "--keep-tmp"
      switch :verbose
      switch :debug
      flag   "--commit="
      flag   "--before="
    end

    ENV["HOMEBREW_UPDATE_TEST"] = "1"

    branch = if args.to_tag?
      ENV["HOMEBREW_UPDATE_TO_TAG"] = "1"
      "stable"
    else
      "master"
    end

    start_commit, end_commit = nil
    cd HOMEBREW_REPOSITORY do
      start_commit = if commit = args.commit
        commit
      elsif date = args.before
        Utils.popen_read("git", "rev-list", "-n1", "--before=#{date}", "origin/master").chomp
      elsif args.to_tag?
        tags = Utils.popen_read("git", "tag", "--list", "--sort=-version:refname")
        previous_tag = tags.lines[1]
        previous_tag ||= begin
          if (HOMEBREW_REPOSITORY/".git/shallow").exist?
            safe_system "git", "fetch", "--tags", "--depth=1"
            tags = Utils.popen_read("git", "tag", "--list", "--sort=-version:refname")
          elsif OS.linux?
            tags = Utils.popen_read("git tag --list | sort -rV")
          end
          tags.lines[1]
        end
        previous_tag = previous_tag.to_s.chomp
        odie "Could not find previous tag in:\n#{tags}" if previous_tag.empty?
        previous_tag
      else
        Utils.popen_read("git", "rev-parse", "origin/master").chomp
      end
      odie "Could not find start commit!" if start_commit.empty?

      start_commit = Utils.popen_read("git", "rev-parse", start_commit).chomp
      odie "Could not find start commit!" if start_commit.empty?

      end_commit = Utils.popen_read("git", "rev-parse", "HEAD").chomp
      odie "Could not find end commit!" if end_commit.empty?
    end

    puts "Start commit: #{start_commit}"
    puts "End   commit: #{end_commit}"

    mkdir "update-test" do
      curdir = Pathname.new(Dir.pwd)

      oh1 "Setup test environment..."
      # copy Homebrew installation
      safe_system "git", "clone", "--local", "#{HOMEBREW_REPOSITORY}/.git", "."

      # set git origin to another copy
      safe_system "git", "clone", "--local", "--bare", "#{HOMEBREW_REPOSITORY}/.git", "remote.git"
      safe_system "git", "config", "remote.origin.url", "#{curdir}/remote.git"

      # force push origin to end_commit
      safe_system "git", "checkout", "-B", "master", end_commit
      safe_system "git", "push", "--force", "origin", "master"

      # set test copy to start_commit
      safe_system "git", "reset", "--hard", start_commit

      # update ENV["PATH"]
      ENV["PATH"] = PATH.new(ENV["PATH"]).prepend(curdir/"bin")

      # run brew update
      oh1 "Running brew update..."
      safe_system "brew", "update", "--verbose"
      actual_end_commit = Utils.popen_read("git", "rev-parse", branch).chomp
      if start_commit != end_commit && start_commit == actual_end_commit
        raise <<~EOS
          brew update didn't update #{branch}!
          Start commit:        #{start_commit}
          Expected end commit: #{end_commit}
          Actual end commit:   #{actual_end_commit}
        EOS
      end
    end
  ensure
    FileUtils.rm_r "update-test" unless args.keep_tmp?
  end
end