changeset 49886:acdb9a15137c

bundle: when forcing acceptance of incoming delta also accept snapshot

Snapshot where never considered reusable and the unbundling side always tried
to find a delta from them. In the `forced` mode this is counter-productive
because it will either connect two delta-tree that should not be connected or
it will spend potentially a lot of time because creating a full snapshot
anyway.

So in this mode, we accept the full snapshot as is.

This changeset is benchmarked with its children so please do not split them
apart when landing.

--- a/mercurial/revlogutils/deltas.py	Wed Dec 07 20:05:19 2022 +0100
+++ b/mercurial/revlogutils/deltas.py	Tue Dec 06 12:10:31 2022 +0100
@@ -684,6 +684,15 @@
         yield None
         return
 
+    if (
+        cachedelta is not None
+        and nullrev == cachedelta[0]
+        and cachedelta[2] == DELTA_BASE_REUSE_FORCE
+    ):
+        # instruction are to forcibly do a full snapshot
+        yield None
+        return
+
     deltalength = revlog.length
     deltaparent = revlog.deltaparent
     sparse = revlog._sparserevlog