$ git clone -n https://src.fedoraproject.org/rpms/rust-rocket.git /var/lib/mock/f41-build-side-1-3103848-39363/root/chroot_tmpdir/scmroot/rust-rocket
Cloning into '/var/lib/mock/f41-build-side-1-3103848-39363/root/chroot_tmpdir/scmroot/rust-rocket'...
$ git fetch origin 6dec4549842e0cd2468d65936b14da010f3448d9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-rocket
 * [new ref]         6dec4549842e0cd2468d65936b14da010f3448d9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6dec454 Initial import (fedora#2315472).