$ git clone -n https://src.fedoraproject.org/rpms/rust-darling.git /var/lib/mock/f42-build-side-1-3536537-46558/root/chroot_tmpdir/scmroot/rust-darling
Cloning into '/var/lib/mock/f42-build-side-1-3536537-46558/root/chroot_tmpdir/scmroot/rust-darling'...
$ git fetch origin fa664d97731254cf4ae02b8a46887eacf166ee69:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-darling
 * [new ref]         fa664d97731254cf4ae02b8a46887eacf166ee69 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fa664d9 Update to version 0.20.11; Fixes RHBZ#2355879