dirstate-v2: Introduce a docket file .hg/dirstate now only contains some metadata to point to a separate data file named .hg/dirstate.{}.d with a random hexadecimal identifier. For now every update creates a new data file and removes the old one, but later we?ll (usually) append to an existing file. Separating into two files allows doing the "write to a temporary file then atomically rename into destination" dance with only a small docket file, without always rewriting a lot of data. Differential Revision: https://phab.mercurial-scm.org/D11088

--- a/mercurial/upgrade_utils/engine.py	Thu Jul 15 17:24:09 2021 +0200
+++ b/mercurial/upgrade_utils/engine.py	Thu Jul 08 12:18:21 2021 +0200
@@ -643,6 +643,7 @@
     srcrepo.dirstate._use_dirstate_v2 = new == b'v2'
     srcrepo.dirstate._map._use_dirstate_v2 = srcrepo.dirstate._use_dirstate_v2
     srcrepo.dirstate._dirty = True
+    srcrepo.vfs.unlink(b'dirstate')
     srcrepo.dirstate.write(None)
 
     scmutil.writereporequirements(srcrepo, upgrade_op.new_requirements)