$ git clone -n https://src.fedoraproject.org/rpms/corrosion.git /var/lib/mock/f39-build-2278854-55222/root/chroot_tmpdir/scmroot/corrosion
Cloning into '/var/lib/mock/f39-build-2278854-55222/root/chroot_tmpdir/scmroot/corrosion'...
$ git fetch origin d0770bffd50ef200f168e70db6d96384bfabd29a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/corrosion
 * [new ref]         d0770bffd50ef200f168e70db6d96384bfabd29a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d0770bf Set RUSTFLAGS environment variable to ensure it's set correctly