_makelogrevset: avoid match.files() in conditions See 9789b4a7c595 (match: introduce boolean prefix() method, 2014-10-28) for reasons to avoid match.files() in conditions.

walkchangerevs: avoid match.files() in conditions See 9789b4a7c595 (match: introduce boolean prefix() method, 2014-10-28) for reasons to avoid match.files() in conditions.

walkchangerevs: simplify with an 'elif' Since 'match.files()' is interchangeable with 'not match.files()', we can simplify with an 'elif' follwoing the 'if match.always()'.