cmdutil: drop obsolete comment about updating to '.' Obsolete since cf68e2649e0a (status: advertise --abort instead of 'update -C .' to abort a merge, 2018-08-09) and 5b04b6204931 (status: advertise --abort instead of 'update -C .' to abort graft, 2018-08-09). Differential Revision: https://phab.mercurial-scm.org/D5694

mq: slightly simplify check for patched working copy Differential Revision: https://phab.mercurial-scm.org/D5693

localrepo: slightly simplify check for removed parents in _rollback() Differential Revision: https://phab.mercurial-scm.org/D5692

transplant: use bailifchanged() instead of reimplementing it Differential Revision: https://phab.mercurial-scm.org/D5691

revpair: clarify check for empty revset Differential Revision: https://phab.mercurial-scm.org/D5688

revpair: simplify revpair by always relying on smartset.first/last I thinkt the code was written the way it was because it comes from 97b2f26dfc43 (revpair: smartset compatibility, 2014-03-20) and the first/last methods came only later, in 228b0aafb1ce (smartset: add first and last methods, 2014-10-06). Differential Revision: https://phab.mercurial-scm.org/D5687

grep: use set instead of dict with dummy value Differential Revision: https://phab.mercurial-scm.org/D5633

grep: don't look up copy info unless --follow is given If no --follow was given, then the "copy" variable will become None. In that case we would still look up the copy information from the filelog and then ignore it. Let's avoid even looking it up. Differential Revision: https://phab.mercurial-scm.org/D5620

hghave: let OSError with ENOENT through like any other Before this patch, if we get an OSError with ENOENT, we would not re-raise it and would instead run into an undefined variable ("p") soon thereafter. Differential Revision: https://phab.mercurial-scm.org/D5631

cleanup: delete lots of unused local variables These were found by IntelliJ. There are many more, but these seemed pretty safe. Differential Revision: https://phab.mercurial-scm.org/D5629