code: def commit():
      
  
      session_token = request.headers['session_token']
      repository    = request.headers['repository']
  
      #===
      current_user = have_authenticated_user(request.environ['REMOTE_ADDR'], repository, session_token)
      if current_user is False: return fail(user_auth_fail_msg)
  
      #===
      repository_path = config['repositories'][repository]['path']
  
      def with_exclusive_lock():
          if not varify_user_lock(repository_path, session_token): return fail(lock_fail_msg)
  
          #===
          data_store = versioned_storage(repository_path)
          if not data_store.have_active_commit(): return fail(no_active_commit_msg)
  
          result = {}
          if request.headers['mode'] == 'commit':
              new_head = data_store.commit(request.headers['commit_message'], current_user['username'])
              result = {'head' : new_head}
          else:
              data_store.rollback()
  
          # Release the user lock
          update_user_lock(repository_path, None)
          return success(result)
      return lock_access(repository_path, with_exclusive_lock)
docs: Commit changes and release the write lock