$ git clone -n https://src.fedoraproject.org/rpms/rust-darling.git /var/lib/mock/f40-build-2100285-50455/root/chroot_tmpdir/scmroot/rust-darling
Cloning into '/var/lib/mock/f40-build-2100285-50455/root/chroot_tmpdir/scmroot/rust-darling'...
$ git fetch origin 1304633e35e3070f24e230aafe4088a4c26edd13:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-darling
 * [new ref]         1304633e35e3070f24e230aafe4088a4c26edd13 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1304633 Update to version 0.20.3; Fixes RHBZ#2190303