very strange distfile names

[Greg Troxel]

I am updating pkgsrc to 1.20.0 and find that the sources suddenly have _
instead of -.  This seems like a bug, and structural changes are a
packaging speedbump.  Plus the direcotry to which it unpacked has
changed.  I didn't find this in NEWS.  Is this change intended?

-rw-r--r--  1 gdt  users  1954858 Oct  3  2022 /links/distfiles/tahoe-lafs-1.18.0.tar.gz
-rw-r--r--  1 gdt  users  2281905 Jan 18  2024 /links/distfiles/tahoe-lafs-1.19.0.tar.gz
-rw-r--r--  1 gdt  users  2237761 Dec 19 00:21 /links/distfiles/tahoe_lafs-1.20.0.tar.gz