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/tests/test-help.t	Thu Jul 15 17:24:09 2021 +0200
+++ b/tests/test-help.t	Thu Jul 08 12:18:21 2021 +0200
@@ -1008,6 +1008,8 @@
                  dump information about delta chains in a revlog
    debugdirstate
                  show the contents of the current dirstate
+   debugdirstateignorepatternshash
+                 show the hash of ignore patterns stored in dirstate if v2,
    debugdiscovery
                  runs the changeset discovery protocol in isolation
    debugdownload