$ git clone -n https://src.fedoraproject.org/rpms/R-AsioHeaders.git /var/lib/mock/f43-build-58894658-6569073/root/chroot_tmpdir/scmroot/R-AsioHeaders
Cloning into '/var/lib/mock/f43-build-58894658-6569073/root/chroot_tmpdir/scmroot/R-AsioHeaders'...
$ git fetch origin dee2b79e78c3399ec4dbbea4104e6f873c4347ee:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-AsioHeaders
 * [new ref]         dee2b79e78c3399ec4dbbea4104e6f873c4347ee -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dee2b79 R-maint-sig mass rebuild