$ git clone -n https://src.fedoraproject.org/rpms/rust-derive_builder0.12.git /var/lib/mock/f41-build-side-1-2928775-35102/root/chroot_tmpdir/scmroot/rust-derive_builder0.12
Cloning into '/var/lib/mock/f41-build-side-1-2928775-35102/root/chroot_tmpdir/scmroot/rust-derive_builder0.12'...
$ git fetch origin 6249c4984990913a156b578e80e1c00bac8ce50a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-derive_builder0.12
 * [new ref]         6249c4984990913a156b578e80e1c00bac8ce50a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6249c49 compat package no longer needed