$ git clone -n https://src.fedoraproject.org/rpms/R-stringi.git /var/lib/mock/f42-build-side-1-3501324-45974/root/chroot_tmpdir/scmroot/R-stringi
Cloning into '/var/lib/mock/f42-build-side-1-3501324-45974/root/chroot_tmpdir/scmroot/R-stringi'...
$ git fetch origin 768269ddbd6555fc1810e299ce44e48e5d4e0f26:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-stringi
 * [new ref]         768269ddbd6555fc1810e299ce44e48e5d4e0f26 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 768269d R-maint-sig mass rebuild