revlog: fix pure python slicing test when chain contains nullrev The revlog mock used in the test was not behaving the same as its C counterpart.

merge with stable

remotefilelog: fix bug in maybesparsematch returning alwaysmatcher The description of the method says that it should return None if sparse is not used in this repository; since sparse.matcher() returns alwaysmatcher if sparse is not enabled, I'm using that as the signal to return None here to preserve the previous behavior. Differential Revision: https://phab.mercurial-scm.org/D5487

procutil: correct spelling of uninterruptable -> uninterruptible Differential Revision: https://phab.mercurial-scm.org/D5488

help: show advanced, experimental and deprecated extensions with --verbose I noticed that phabricator and absorb weren't showing up, no matter what. There's a related problem where commands for these extensions *do* show up without --verbose. I'm not sure what the point of hiding the extensions, but not the commands is.

help: remove a duplicate category name entry for TOPIC_CATEGORY_NONE

phabricator: assign commands to help categories `phabsend` and `phabupdate` seem pretty close to `email`. `phabread` is a little less close, but can be trivially used to actually import patches.

largefiles: eliminate an unnecessary import of configitems Thanks to Yuya for pointing this out.

exthelper: add some examples for using registrar aliases Maybe it's my general lack of python knowledge, but how to use these would be way too obscure for me otherwise.

exthelper: reintroduce the ability to register filesets Same mechanism as revsets earlier in this series. The LFS extension is updated to provide test coverage.