dirstate-v2: Add a new experimental `exp-dirstate-v2` repository requirement This requirement is added to `.hg/requires` when creating a new repository if Rust extensions are enabled and the `format.exp-dirstate-v2` config is set. Nothing yet changes based on this requirement, but its mere presence affects some tests (for example if they print `.hg/requires`). The next two changesets update tests? expected outputs accordingly. There is no CI so far that enables this configuration. Differential Revision: https://phab.mercurial-scm.org/D10716

--- a/mercurial/dirstate.py	Fri Apr 16 00:16:43 2021 +0200
+++ b/mercurial/dirstate.py	Wed May 19 13:14:59 2021 +0200
@@ -39,6 +39,8 @@
 parsers = policy.importmod('parsers')
 rustmod = policy.importrust('dirstate')
 
+SUPPORTS_DIRSTATE_V2 = rustmod is not None
+
 propertycache = util.propertycache
 filecache = scmutil.filecache
 _rangemask = 0x7FFFFFFF