$ git clone -n https://src.fedoraproject.org/rpms/R-rvest.git /var/lib/mock/f38-build-side-42-init-devel-1392155-30890/root/chroot_tmpdir/scmroot/R-rvest
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1392155-30890/root/chroot_tmpdir/scmroot/R-rvest'...
$ git fetch origin f6681e8195a725755f8077e078202a4cbfab4e3e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-rvest
 * [new ref]         f6681e8195a725755f8077e078202a4cbfab4e3e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f6681e8 R-maint-sig mass rebuild