filemerge: put temporary files in single temp dir by default The feature introduced in D2888 seems like a pure improvement to me. It makes the names' of temporary file easier to read. Let's have it always enabled. I also removed the config option for the path prefix because it doesn't seem useful. I asked Kyle (the author of the feature) about it and he couldn't think of a reason to keep it. I suspect it was just that we to have a config to turn it on/off while it was experimental, so it might as well be a configurable prefix then. Differential Revision: https://phab.mercurial-scm.org/D12171

--- a/mercurial/configitems.py	Tue Feb 15 05:20:46 2022 +0100
+++ b/mercurial/configitems.py	Fri Feb 11 16:52:48 2022 -0800
@@ -1042,11 +1042,6 @@
 )
 coreconfigitem(
     b'experimental',
-    b'mergetempdirprefix',
-    default=None,
-)
-coreconfigitem(
-    b'experimental',
     b'mmapindexthreshold',
     default=None,
 )