old_contents: import subprocess
  import time
  
  from setuptools.command.egg_info import egg_info
  
  
  class EggInfoFromGit(egg_info):
      """Tag the build with git commit timestamp.
  
      If a build tag has already been set (e.g., "egg_info -b", building
      from source package), leave it alone.
      """
  
      def git_timestamp_tag(self):
          gitinfo = subprocess.check_output(
              ['git', 'log', '--first-parent', '--max-count=1',
               '--format=format:%ct', '.']).strip()
          return time.strftime('.%Y%m%d%H%M%S', time.gmtime(int(gitinfo)))
  
      def tags(self):
          if self.tag_build is None:
              try:
                  self.tag_build = self.git_timestamp_tag()
              except subprocess.CalledProcessError:
                  pass
          return egg_info.tags(self)
      vtags = property(tags)
  
new_contents: import subprocess
  import time
  import pkg_resources
  from setuptools.command.egg_info import egg_info
  
  SETUPTOOLS_VER = pkg_resources.get_distribution(
      "setuptools").version.split('.')
  
  RECENT_SETUPTOOLS = int(SETUPTOOLS_VER[0]) > 40 or (
      int(SETUPTOOLS_VER[0]) == 40 and int(SETUPTOOLS_VER[1]) > 0) or (
          int(SETUPTOOLS_VER[0]) == 40 and int(SETUPTOOLS_VER[1]) == 0 and
          int(SETUPTOOLS_VER[2]) > 0)
  
  class EggInfoFromGit(egg_info):
      """Tag the build with git commit timestamp.
  
      If a build tag has already been set (e.g., "egg_info -b", building
      from source package), leave it alone.
      """
  
      def git_timestamp_tag(self):
          gitinfo = subprocess.check_output(
              ['git', 'log', '--first-parent', '--max-count=1',
               '--format=format:%ct', '.']).strip()
          return time.strftime('.%Y%m%d%H%M%S', time.gmtime(int(gitinfo)))
  
      def tags(self):
          if self.tag_build is None:
              try:
                  self.tag_build = self.git_timestamp_tag()
              except subprocess.CalledProcessError:
                  pass
          return egg_info.tags(self)
  
      if RECENT_SETUPTOOLS:
          vtags = property(tags)
  
subject: support older setuptools