git_commit_sha

# File lib/bundler/build_metadata.rb, line 27
    def self.git_commit_sha
      return @git_commit_sha if @git_commit_sha

      # If Bundler has been installed without its .git directory and without a
      # commit instance variable then we can't determine its commits SHA.
      git_dir = File.join(File.expand_path("../../..", __FILE__), ".git")
      if File.directory?(git_dir)
        return @git_commit_sha = Dir.chdir(git_dir) { `git rev-parse --short HEAD`.strip.freeze }
      end

      # If Bundler is a submodule in RubyGems, get the submodule commit
      git_sub_dir = File.join(File.expand_path("../../../..", __FILE__), ".git")
      if File.directory?(git_sub_dir)
        return @git_commit_sha = Dir.chdir(git_sub_dir) do
          `git ls-tree --abbrev=8 HEAD bundler`.split(/\s/).fetch(2, "").strip.freeze
        end
      end

      @git_commit_sha ||= "unknown"
    end