tests/test-revert-unknown.t

context: avoid breaking already fixed self._status at ctx.status()

Before this patch, "status()" on "workingcommitctx" with "always
match" object causes breaking "self._status" in
"workingctx._buildstatus()", because "workingctx._buildstatus()"
caches the result of "dirstate.status()" into "self._status" for
efficiency, even though it should be fixed at construction for
committing.

For example, template function "diff()" without any patterns in
"committemplate" implies "status()" on "workingcommitctx" with "always
match" object, via "basectx.diff()" and "patch.diff()".

Then, broken "self._status" causes committing unexpected files.

To avoid breaking already fixed "self._status" at "ctx.status()", this
patch overrides "_buildstatus" in "workingcommitctx".

This patch doesn't write out the result of template function "diff()"
in "committemplate" in "test-commit.t", because matching against files
to be committed still has an issue fixed in subsequent patch.

  $ hg init
  $ touch unknown

  $ touch a
  $ hg add a
  $ hg ci -m "1"

  $ touch b
  $ hg add b
  $ hg ci -m "2"

Should show unknown

  $ hg status
  ? unknown
  $ hg revert -r 0 --all
  removing b

Should show unknown and b removed

  $ hg status
  R b
  ? unknown

Should show a and unknown

  $ ls
  a
  unknown