Oh, so *that's* what went wrong! This is entirely my fault.

I was pushing one of the regressions to 2.063, and github kept saying:

----------------------------------
mercury ~/dpl/dmd> git push origin 2.063
To git@github.com:D-Programming-Language/dmd.git
 ! [rejected]        2.063 -> 2.063 (non-fast-forward)
error: failed to push some refs to 'git@github.com:D-Programming-Language/dmd.git'
To prevent you from losing history, non-fast-forward updates were rejected
Merge the remote changes before pushing again.  See the 'Note about
fast-forwards' section of 'git push --help' for details.
-----------------------------------

git status, of course, told me nothing, so I tried git push -f.

Sorry.