configitems: add a default value for "merge-tools.xxx.regappend" When trying to figure out how `hg help -v` took the Set interpolation path in f09bc2ed9100, I turned on devel warnings and noticed this (unrelated) warning: devel-warn: specifying a mismatched default value for a registered config item: 'merge-tools.beyondcompare4.regappend' '' at: c:\Users\Matt\hg\mercurial\filemerge.py:46 (_toolstr) The previous default value for this config was `None`, but that slightly complicates the code at the only site it is used, referenced above.

--- a/mercurial/configitems.py	Mon Nov 21 15:04:42 2022 -0500
+++ b/mercurial/configitems.py	Sun Nov 20 23:09:12 2022 -0500
@@ -1786,6 +1786,13 @@
 )
 coreconfigitem(
     b'merge-tools',
+    br'.*\.regappend$',
+    default=b"",
+    generic=True,
+    priority=-1,
+)
+coreconfigitem(
+    b'merge-tools',
     br'.*\.symlink$',
     default=False,
     generic=True,