tests/test-diff-issue2761.t

dirstate-v2: Drop parent directory cache when removing a dirstate node

The premise of the directory cache is that the dirstate contains child nodes
for every entry that `read_dir` would return. When removing nodes, that may
not be the case anymore so the cache should be invalidated.

Differential Revision: https://phab.mercurial-scm.org/D10829

Test issue2761

  $ hg init

  $ touch to-be-deleted
  $ hg add
  adding to-be-deleted
  $ hg ci -m first
  $ echo a > to-be-deleted
  $ hg ci -m second
  $ rm to-be-deleted
  $ hg diff -r 0

Same issue, different code path

  $ hg up -C
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ touch does-not-exist-in-1
  $ hg add
  adding does-not-exist-in-1
  $ hg ci -m third
  $ rm does-not-exist-in-1
  $ hg diff -r 1