dirstate: subclass the new dirstate Protocol class

Behold the chaos that ensues.  We'll use the generated *.pyi files to apply type
annotations to the interface, and see how much agrees with the documentation.

Since the CamelCase name was used to try to work around pytype issues with zope
interfaces and is a new innovation this cycle (see c1d7ac70980b), drop the
CamelCase name.  I think the Protocol classes *should* be CamelCase, but that
can be done later in one pass.  For now, the CamelCase alias is extra noise in
the *.pyi files.

hgext/git/dirstate.py

@@ -18,7 +18,6 b' from mercurial.dirstateutils import ('
 )
 from mercurial.interfaces import (
     dirstate as intdirstate,
-    util as interfaceutil,
 )
 
 from . import gitutil
@@ -73,8 +72,7 b' if pygit2:'
     }
 
 
[e-mail](intdirstate.idirstate)
-class gitdirstate:
+class gitdirstate(intdirstate.idirstate):
     def __init__(self, ui, vfs, gitrepo, use_dirstate_v2):
         self._ui = ui
         self._root = os.path.dirname(vfs.base)

mercurial/dirstate.py

@@ -11,7 +11,6 b' import collections'
 import contextlib
 import os
 import stat
-import typing
 import uuid
 
 from .i18n import _
@@ -38,7 +37,6 b' from .dirstateutils import ('
 
 from .interfaces import (
     dirstate as intdirstate,
-    util as interfaceutil,
 )
 
 parsers = policy.importmod('parsers')
@@ -136,7 +134,7 b' CHANGE_TYPE_PARENTS = "parents"'
 CHANGE_TYPE_FILES = "files"
 
 
-class DirState:
+class dirstate(intdirstate.idirstate):
     # used by largefile to avoid overwritting transaction callback
     _tr_key_suffix = b''
 
@@ -1808,9 +1806,3 b' class DirState:'
             entry = self.get_entry(f)
             if not entry.p1_tracked:
                 yield missing_from_ds % (f, node.short(p1))
-
-
-dirstate = interfaceutil.implementer(intdirstate.idirstate)(DirState)
-
-if typing.TYPE_CHECKING:
-    dirstate = DirState