[Fontconfig] Changing the default pattern weight via config?

[Thomas Sibley]

Hi,

With version 2.11.1, the default weight for patterns missing a weight
changed from medium to regular.¹  Is there any way to replicate that
change in earlier versions using local configuration files?

I've tried a number of ways with <match> and friends, but I am unable to
force a pattern without a weight to yield weight=regular while still
allowing a pattern with a weight to pass through the <match> unchanged.
The crux of the problem is that I can't determine a way to specifically
match a property with no value (which I believe is what I need to do to
change the pattern before it gets filled in with defaults).

Any pointers would be appreciated.  If it's known to be impossible,
that's also useful to know.  :-)

Cheers,
Thomas

¹ Some context here:
  https://lists.freedesktop.org/archives/fontconfig/2013-October/004978.html