I noticed that btrfs-progs was updated to 4.8.2 on core-updates twice.

Commited to core-updates:
http://git.savannah.gnu.org/cgit/guix.git/commit/?h=core-updates&id=f02fb6dd6b6dbf91c3497a086bab5d9e791b2468

Commited on master and then merged into core-updates:
http://git.savannah.gnu.org/cgit/guix.git/commit/?h=core-updates&id=6270769dc216fc6a2f54ca77d3090e3e610ade1c

I've experienced similar shenanigans while testing my own merges. I
wonder if there is anything we can do to avoid this?