tests/test-remotefilelog-bad-configs.t

exthelper: reintroduce the ability to register revsets

I think this is what Yuya and Boris agreed on.[1]  This happens *after* the
extsetup phase now (and after the _aftercallback notifications).  But this is
trivial, mergeable between exthelper instances, and doesn't need to have the
extension name supplied when registering.

The test needed updating so that extsetup() takes a `ui` argument, as exthelper
isn't trying to be backward compatible with 1.3.1.

[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2018-December/125888.html

#require no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ echo y > y
  $ echo z > z
  $ hg commit -qAm xy

  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)
  $ cd shallow

Verify error message when noc achepath specified
  $ hg up -q null
  $ cp $HGRCPATH $HGRCPATH.bak
  $ grep -v cachepath < $HGRCPATH.bak > tmp
  $ mv tmp $HGRCPATH
  $ hg up tip
  abort: could not find config option remotefilelog.cachepath
  [255]
  $ mv $HGRCPATH.bak $HGRCPATH

Verify error message when no fallback specified

  $ hg up -q null
  $ rm .hg/hgrc
  $ clearcache
  $ hg up tip
  3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)
  abort: no remotefilelog server configured - is your .hg/hgrc trusted?
  [255]