tests/test-empty.t

manifest: make one use of _mancache avoid manifestctxs

In a future patch we will change manifestctx and treemanifestctx to no longer
derive from manifestdict and treemanifest, respectively. This means that
consumers of the _mancache will now need to be aware of the different between
the two, until we get rid of the manifest entirely and the _mancache becomes
only filled with ctxs.

This fixes one case of it that can be fixed by using the other cache. Future
patches will address the others uses using the upcoming manifestctx.read()
function.

Create an empty repo:

  $ hg init a
  $ cd a

Try some commands:

  $ hg log
  $ hg grep wah
  [1]
  $ hg manifest
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  0 files, 0 changesets, 0 total revisions

Check the basic files created:

  $ ls .hg
  00changelog.i
  requires
  store

Should be empty:

  $ ls .hg/store

Poke at a clone:

  $ cd ..
  $ hg clone a b
  updating to branch default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd b
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  0 files, 0 changesets, 0 total revisions
  $ ls .hg
  00changelog.i
  hgrc
  requires
  store

Should be empty:

  $ ls .hg/store

  $ cd ..