tests/test-remotefilelog-bad-configs.t

rust-cpython: prepare for writing tests that require libpython

What I wanted is to disable the "cpython/extension-module<ver>" feature
while building tests executable, but that seems not doable. Instead,
this patch adds new features dedicated for tests.

The make rule is extracted so that we can easily run cargo tests.

Added a minimal test of ref-sharing as an example. More tests will follow.

#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]