$ git clone -n https://src.fedoraproject.org/rpms/rust-arbitrary.git /var/lib/mock/f38-build-side-43-rust-devel-1416594-31457/root/chroot_tmpdir/scmroot/rust-arbitrary
Cloning into '/var/lib/mock/f38-build-side-43-rust-devel-1416594-31457/root/chroot_tmpdir/scmroot/rust-arbitrary'...
$ git fetch origin 9842f63783f10ab4bc78180fb17ae90534218b4f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-arbitrary
 * [new ref]         9842f63783f10ab4bc78180fb17ae90534218b4f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9842f63 Update to version 1.3.0; Fixes RHBZ#2177901