tests/test-rhg-sparse-narrow.t

interfaces: add the optional `bdiff.xdiffblocks()` method

PyCharm flagged where this was called on the protocol class in `mdiff.py` in the
previous commit, but pytype completely missed it.  PyCharm is correct here, but
I'm committing this separately to highlight this potential problem- some of the
implementations don't implement _all_ of the methods the others do, and there's
not a great way to indicate on a protocol class that a method or attribute is
optional- that's kinda the opposite of what static typing is about.

Making the method an `Optional[Callable]` attribute works here, and keeps both
PyCharm and pytype happy, and the generated `mdiff.pyi` and `modules.pyi` look
reasonable.  We might be getting a little lucky, because the method isn't
invoked directly- it is returned from another method that selects which block
function to use.  Except since it is declared on the protocol class, every
module needs this attribute (in theory, but in practice this doesn't seem to be
checked), so the check for it on the module has to change from `hasattr()` to
`getattr(..., None)`.  We defer defining the optional attrs to the type checking
phase as an extra precaution- that way it isn't an attr with a `None` value at
runtime if someone is still using `hasattr()`.

As to why pytype missed this, I have no clue.  The generated `mdiff.pyi` even
has the global variable typed as `bdiff: intmod.BDiff`, so uses of it really
should comply with what is on the class, protocol class or not.

#require rhg

  $ NO_FALLBACK="env RHG_ON_UNSUPPORTED=abort"

Rhg works well when sparse working copy is enabled.

  $ cd "$TESTTMP"
  $ hg init repo-sparse
  $ cd repo-sparse
  $ cat > .hg/hgrc <<EOF
  > [extensions]
  > sparse=
  > EOF

  $ echo a > show
  $ echo x > hide
  $ mkdir dir1 dir2
  $ echo x > dir1/x
  $ echo y > dir1/y
  $ echo z > dir2/z

  $ hg ci -Aqm 'initial'
  $ hg debugsparse --include 'show'
  $ ls -A
  .hg
  show

  $ tip=$(hg log -r . --template '{node}')
  $ $NO_FALLBACK rhg files -r "$tip"
  dir1/x
  dir1/y
  dir2/z
  hide
  show
  $ $NO_FALLBACK rhg files
  show

  $ $NO_FALLBACK rhg cat -r "$tip" hide
  x

  $ cd ..

We support most things when narrow is enabled, too, with a couple of caveats.

  $ . "$TESTDIR/narrow-library.sh"
  $ real_hg=$RHG_FALLBACK_EXECUTABLE

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > narrow=
  > EOF

  $ hg clone --narrow  ./repo-sparse repo-narrow --include dir1
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 2 changes to 2 files
  new changesets 6d714a4a2998
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd repo-narrow

  $ $NO_FALLBACK rhg cat -r "$tip" dir1/x
  x
  $ "$real_hg" cat -r "$tip" dir1/x
  x

TODO: bad error message

  $ $NO_FALLBACK rhg cat -r "$tip" hide
  abort: invalid revision identifier: 6d714a4a2998cbfd0620db44da58b749f6565d63
  [255]
  $ "$real_hg" cat -r "$tip" hide
  [1]

A naive implementation of `rhg files` would leak the paths that are supposed
to be hidden by narrow.

  $ $NO_FALLBACK rhg files -r "$tip"
  dir1/x
  dir1/y
  $ "$real_hg" files -r "$tip"
  dir1/x
  dir1/y

The working copy version works with narrow correctly

  $ $NO_FALLBACK rhg files
  dir1/x
  dir1/y
  $ "$real_hg" files
  dir1/x
  dir1/y

Hg status needs to do some filtering based on narrow spec

  $ mkdir dir2
  $ touch dir2/q
  $ "$real_hg" status
  $ $NO_FALLBACK rhg --config rhg.status=true status

Adding "orphaned" index files:

  $ (cd ..; cp repo-sparse/.hg/store/data/hide.i repo-narrow/.hg/store/data/hide.i)
  $ (cd ..; mkdir repo-narrow/.hg/store/data/dir2; cp repo-sparse/.hg/store/data/dir2/z.i repo-narrow/.hg/store/data/dir2/z.i)
  $ "$real_hg" verify -q

  $ "$real_hg" files -r "$tip"
  dir1/x
  dir1/y

# TODO: even though [hg files] hides the orphaned dir2/z, [hg cat] still shows it.
# rhg has the same issue, but at least it's not specific to rhg.
# This is despite [hg verify] succeeding above.

  $ $NO_FALLBACK rhg cat -r "$tip" dir2/z
  z
  $ "$real_hg" cat -r "$tip" dir2/z
  z