$ git clone -n https://src.fedoraproject.org/rpms/rust-serde_derive.git /var/lib/mock/f40-build-2657994-66917/root/chroot_tmpdir/scmroot/rust-serde_derive
Cloning into '/var/lib/mock/f40-build-2657994-66917/root/chroot_tmpdir/scmroot/rust-serde_derive'...
$ git fetch origin c3f7eb7a75d0f589c318f2b49f471c7f4fa5ef97:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-serde_derive
 * [new ref]         c3f7eb7a75d0f589c318f2b49f471c7f4fa5ef97 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c3f7eb7 Update to version 1.0.197; Fixes RHBZ#2265027