merge: don't call update hook when using in-memory context I'm pretty sure many hook implementors will assume that they can inspect the working copy and/or dirstate parents when the hook is called, so I don't think we should call the hook when using an in-memory context. The new behavior matches that of the preupdate hook. Differential Revision: https://phab.mercurial-scm.org/D7898

--- a/mercurial/merge.py	Thu Jan 23 13:10:48 2020 -0800
+++ b/mercurial/merge.py	Wed Jan 15 15:07:43 2020 -0800
@@ -2574,7 +2574,7 @@
     if not branchmerge:
         sparse.prunetemporaryincludes(repo)
 
-    if not partial:
+    if updatedirstate:
         repo.hook(
             b'update', parent1=xp1, parent2=xp2, error=stats.unresolvedcount
         )