anchor.diff:  }
   
   class Git {
  -  static const _shaRegexPattern = '[a-f0-9]{40}';
  -  static final _shaRegEx = new RegExp(r'^' + _shaRegexPattern + r'$');
  +  static const _SHA_REGEX_PATTERN = '[a-f0-9]{40}';
  +  static final _shaRegEx = new RegExp(r'^' + _SHA_REGEX_PATTERN + r'$');
   
     static bool isValidSha(String value) {
       return _shaRegEx.hasMatch(value);
  
positive.code: 
  class TreeEntry {
    static final _lsTreeLine = r'^([0-9]{6}) (blob|tree) ('
        + Git._shaRegexPattern
        + ')\t(\\S.*\\S)\$';
  
    static final _lsTreeRegEx = new RegExp(_lsTreeLine);
  
negative.code:  * Represents the output from `git show-ref`
   */
  class CommitReference {
    static final RegExp _lsRemoteRegExp = new RegExp('^(${Git._SHA_REGEX_PATTERN}) (.+)\$');
  
    final String sha;
    final String reference;
  