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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def scan_diff( self, diff, baseline_filename='', last_commit_hash='', repo_name='', ):
 """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 """

        # 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,
                    ),
                )