public Depend(PathImpl source,long digest,boolean requireSource){
  this(source);
  long newDigest=source.getCrc64();
  _requireSource=requireSource;
  if (newDigest == digest) {
  }
 else   if (!requireSource && newDigest == 0) {
  }
 else   if (newDigest == 0) {
    if (log.isLoggable(Level.FINE))     log.fine(_source.getNativePath() + " source is deleted.");
    _isDigestModified=true;
  }
 else {
    _isDigestModified=true;
  }
}

public Depend ( PathImpl source , long digest , boolean requireSource ) { this ( source ) ; long newDigest = source . getCrc64 ( ) ; _requireSource = requireSource ; if ( newDigest == digest ) { } else if ( ! requireSource && newDigest == 0 ) { } else if ( newDigest == 0 ) { if ( log . isLoggable ( Level . FINE ) ) log . fine ( _source . getNativePath ( ) + " source is deleted." ) ; _isDigestModified = true ; } else { _isDigestModified = true ; } }
create a new dependency with a given digest .
