code: def _reverse(self):
      
      for p in self.items:
        for h in p.hunks:
          h.startsrc, h.starttgt = h.starttgt, h.startsrc
          h.linessrc, h.linestgt = h.linestgt, h.linessrc
          for i,line in enumerate(h.text):
            # need to use line[0:1] here, because line[0]
            # returns int instead of bytes on Python 3
            if line[0:1] == b'+':
              h.text[i] = b'-' + line[1:]
            elif line[0:1] == b'-':
              h.text[i] = b'+' +line[1:]
docs: reverse patch direction (this doesn't touch filenames)