code: def scan_diff(
          self,
          diff,
          baseline_filename='',
          last_commit_hash='',
          repo_name='',
      ):
          
          # Local imports, so that we don't need to require unidiff for versions of
          # detect-secrets that don't use it.
          from unidiff import PatchSet
          from unidiff.errors import UnidiffParseError
  
          try:
              patch_set = PatchSet.from_string(diff)
          except UnidiffParseError:  # pragma: no cover
              alert = {
                  'alert': 'UnidiffParseError',
                  'hash': last_commit_hash,
                  'repo_name': repo_name,
              }
              log.error(alert)
              raise
  
          if self.exclude_files:
              regex = re.compile(self.exclude_files, re.IGNORECASE)
  
          for patch_file in patch_set:
              filename = patch_file.path
              # If the file matches the exclude_files, we skip it
              if self.exclude_files and regex.search(filename):
                  continue
  
              if filename == baseline_filename:
                  continue
  
              for results, plugin in self._results_accumulator(filename):
                  results.update(
                      self._extract_secrets_from_patch(
                          patch_file,
                          plugin,
                          filename,
                      ),
                  )
docs: For optimization purposes, our scanning strategy focuses on looking
          at incremental differences, rather than re-scanning the codebase every time.
          This function supports this, and adds information to self.data.
  
          :type diff: str
          :param diff: diff string.
                       e.g. The output of `git diff <fileA> <fileB>`
  
          :type baseline_filename: str
          :param baseline_filename: if there are any baseline secrets, then the baseline
                                    file will have hashes in them. By specifying it, we
                                    can skip this clear exception.
  
          :type last_commit_hash: str
          :param last_commit_hash: used for logging only -- the last commit hash we saved
  
          :type repo_name: str
          :param repo_name: used for logging only -- the name of the repo