docs: def _relativePath(self, fullPath):
          """ Return fullPath relative to Store directory.
  
          Return fullPath if fullPath is not inside directory.
  
          Return None if fullPath is outside our scope.
          """
          if fullPath is None:
              return None
  
          assert fullPath.startswith("/"), fullPath
  
          path = os.path.relpath(fullPath, self.userPath)
  
          if not path.startswith("../"):
              return path
          elif self.ignoreExtraVolumes:
              return None
          else:
              return fullPath