$ git clone -n https://src.fedoraproject.org/rpms/R-V8.git /var/lib/mock/f45-build-5964-345/root/chroot_tmpdir/scmroot/R-V8
Cloning into '/var/lib/mock/f45-build-5964-345/root/chroot_tmpdir/scmroot/R-V8'...
$ git fetch origin 8233f8ce7592af98dd4bbe1f0631f5191cc1622c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-V8
 * [new ref]         8233f8ce7592af98dd4bbe1f0631f5191cc1622c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8233f8c Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild