$ git clone -n https://src.fedoraproject.org/rpms/R-httpuv.git /var/lib/mock/f42-build-3530696-46321/root/chroot_tmpdir/scmroot/R-httpuv
Cloning into '/var/lib/mock/f42-build-3530696-46321/root/chroot_tmpdir/scmroot/R-httpuv'...
$ git fetch origin cdb5977f714f3c1c453075bfd0b10917c3b84637:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-httpuv
 * [new ref]         cdb5977f714f3c1c453075bfd0b10917c3b84637 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cdb5977 R-maint-sig mass rebuild