$ git clone -n https://src.fedoraproject.org/rpms/R-gargle.git /var/lib/mock/f42-build-side-1-3500315-45970/root/chroot_tmpdir/scmroot/R-gargle
Cloning into '/var/lib/mock/f42-build-side-1-3500315-45970/root/chroot_tmpdir/scmroot/R-gargle'...
$ git fetch origin 7ea8e5477eeec6b8b8a791e43fae82e039178a64:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-gargle
 * [new ref]         7ea8e5477eeec6b8b8a791e43fae82e039178a64 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7ea8e54 R-maint-sig mass rebuild