revlog: return 0 for the fast_rank of nullrev
By convention, the rank of the null revision is 0. This particular revision is
never "physically" stored in the changelog, so it is a special case.
For consistency, the value `None` is still being returned for revlogs which do
not store the fast_rank property for any revision.
Differential Revision: https://phab.mercurial-scm.org/D12208
--- a/mercurial/revlog.py Wed Mar 02 18:42:00 2022 -0800
+++ b/mercurial/revlog.py Mon Feb 21 15:53:03 2022 +0100
@@ -869,8 +869,10 @@
the revlog which do not persist the rank.
"""
rank = self.index[rev][ENTRY_RANK]
- if rank == RANK_UNKNOWN:
+ if self._format_version != CHANGELOGV2 or rank == RANK_UNKNOWN:
return None
+ if rev == nullrev:
+ return 0 # convention
return rank
def chainbase(self, rev):