text: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  # Copyright 2016 OpenMarket Ltd
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import logging
  import os
  import subprocess
  
  logger = logging.getLogger(__name__)
  
  
  def get_version_string(module):
      try:
          null = open(os.devnull, 'w')
          cwd = os.path.dirname(os.path.abspath(module.__file__))
          try:
              git_branch = subprocess.check_output(
                  ['git', 'rev-parse', '--abbrev-ref', 'HEAD'],
                  stderr=null,
                  cwd=cwd,
              ).strip().decode('ascii')
              git_branch = "b=" + git_branch
          except subprocess.CalledProcessError:
              git_branch = ""
  
          try:
              git_tag = subprocess.check_output(
                  ['git', 'describe', '--exact-match'],
                  stderr=null,
                  cwd=cwd,
              ).strip().decode('ascii')
              git_tag = "t=" + git_tag
          except subprocess.CalledProcessError:
              git_tag = ""
  
          try:
              git_commit = subprocess.check_output(
                  ['git', 'rev-parse', '--short', 'HEAD'],
                  stderr=null,
                  cwd=cwd,
              ).strip().decode('ascii')
          except subprocess.CalledProcessError:
              git_commit = ""
  
          try:
              dirty_string = "-this_is_a_dirty_checkout"
              is_dirty = subprocess.check_output(
                  ['git', 'describe', '--dirty=' + dirty_string],
                  stderr=null,
                  cwd=cwd,
              ).strip().decode('ascii').endswith(dirty_string)
  
              git_dirty = "dirty" if is_dirty else ""
          except subprocess.CalledProcessError:
              git_dirty = ""
  
          if git_branch or git_tag or git_commit or git_dirty:
              git_version = ",".join(
                  s for s in
                  (git_branch, git_tag, git_commit, git_dirty,)
                  if s
              )
  
              return (
                  "%s (%s)" % (
                      module.__version__, git_version,
                  )
              )
      except Exception as e:
          logger.info("Failed to check for git repository: %s", e)
  
      return module.__version__
  