diff -r 1a7d12c82057 -r 62a0b5daa15f mercurial/commands.py
--- a/mercurial/commands.py	Thu May 07 16:50:26 2020 -0400
+++ b/mercurial/commands.py	Mon Feb 01 11:57:18 2021 -0500
@@ -2576,7 +2576,9 @@
                 },
                 b'diff --merge',
             ):
+                repo.ui.pushbuffer()
                 mergemod.merge(pctx2, wc=wctx)
+                repo.ui.popbuffer()
             ctx1 = wctx
         else:
             ctx1 = ctx2.p1()