# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@octobus.net>
# Date 2023-12-07 02:49:48
# Node ID 1486d8c63f641ba28a2937b61b3feed04d6a50c4
# Parent  e306d552dfb126efec571c5834400c84809c7efb

persistent-nodemap: avoid writing nodemap for empty revlog

The format cannot encode the lack of tip_rev.

There is currently nothing known to write such empty nodemap right now, but the
change we are preparing on default reveal this issue. So I had rather fix it on
stable.

diff --git a/mercurial/revlogutils/nodemap.py b/mercurial/revlogutils/nodemap.py
--- a/mercurial/revlogutils/nodemap.py
+++ b/mercurial/revlogutils/nodemap.py
@@ -163,6 +163,8 @@ def delete_nodemap(tr, repo, revlog):
 
 def persist_nodemap(tr, revlog, pending=False, force=False):
     """Write nodemap data on disk for a given revlog"""
+    if len(revlog.index) <= 0:
+        return
     if getattr(revlog, 'filteredrevs', ()):
         raise error.ProgrammingError(
             "cannot persist nodemap of a filtered changelog"