$ git clone -n https://src.fedoraproject.org/rpms/R-htmlwidgets.git /var/lib/mock/f42-build-side-1-3500310-45970/root/chroot_tmpdir/scmroot/R-htmlwidgets
Cloning into '/var/lib/mock/f42-build-side-1-3500310-45970/root/chroot_tmpdir/scmroot/R-htmlwidgets'...
$ git fetch origin 65f5bf6f91843f4766fa6bcd5909981fd32aa8c7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-htmlwidgets
 * [new ref]         65f5bf6f91843f4766fa6bcd5909981fd32aa8c7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 65f5bf6 R-maint-sig mass rebuild