log: allow matchfn to be non-null even if both --patch/--stat are off This makes the next patch slightly simpler.

log: replace "not pats" with matcher attribute for consistency We use match.always() in _makelogrevset(). match.always() is identical to "not pats" here since scmutil.matchandpats() empties pats in that case.

log: follow file history across copies even with -rREV (BC) (issue4959) Still it falls back to changelog path if glob patterns or missing paths are specified. This will be changed later. .. bc:: ``log --follow -rREV FILE..`` now follows file history across copies and renames.

log: resolve --follow thoroughly in getlogrevs() This makes sense because --follow isn't really an option to filter revisions, but an option to extend revisions to be filtered. _fileancestors() is a minimal copy of revset._follow(). They are slightly different in that which revision the matcher sees. _fileancestors() also uses ctx.walk() instead of ctx.manifest().walk() to show a better warning on bad match, which will be tested later.

log: extract function that processes log file patterns We'll need a matcher to compute revs followed from the given patterns.

log: resolve --follow with -rREV in cmdutil.getlogrevs() This also fixes alias expansion. Before, reverse() could be overridden by user alias. This isn't processed at _logrevs() as we'll need starting revisions to parse file patterns. See the subsequent patches for details.

log: remove dead code to follow descendants if ascending revisions specified It's been disabled since 8b4b9ee6001a "log: make -fr show complete history from the given revs" 2015-02-06, and we've got no bug report regarding this exact behavior. For details what the heck "followdescendants" is, please see the issue comment: https://bz.mercurial-scm.org/show_bug.cgi?id=4959#c72 "'rev(%d)' % startrev" can be replaced with '.' since revs are 'reversed(:.)'.