ui: add a context manager for silencing the ui (pushbuffer+popbuffer) We often silence the ui by calling `ui.pushbuffer()` followed (a later in the code) by `ui.popbuffer()`. These places can be identified by the fact that they ignore the output returned from `ui.popbuffer()`. Let's create a context manager for these cases, to avoid repetition, and to avoid accidentally leaving the ui silent on exceptions. I deliberately called the new function `silent()` instead of `buffered()`, because it's just an implementation detail that it uses `pushbuffer()` and `popbuffer()`. We could later optimize it to not buffer the output. Differential Revision: https://phab.mercurial-scm.org/D10884

--- a/mercurial/logcmdutil.py	Fri Jun 18 14:17:43 2021 -0700
+++ b/mercurial/logcmdutil.py	Fri Jun 18 15:48:51 2021 -0700
@@ -93,9 +93,8 @@
             },
             b"merge-diff",
         ):
-            repo.ui.pushbuffer()
-            merge.merge(ctx.p2(), wc=wctx)
-            repo.ui.popbuffer()
+            with repo.ui.silent():
+                merge.merge(ctx.p2(), wc=wctx)
         return wctx
     else:
         return ctx.p1()