$ git clone -n https://src.fedoraproject.org/rpms/rust-derive_builder_core.git /var/lib/mock/f40-build-2655314-66910/root/chroot_tmpdir/scmroot/rust-derive_builder_core
Cloning into '/var/lib/mock/f40-build-2655314-66910/root/chroot_tmpdir/scmroot/rust-derive_builder_core'...
$ git fetch origin 69439844adfced6eadd20203a0b65ddabe421aac:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-derive_builder_core
 * [new ref]         69439844adfced6eadd20203a0b65ddabe421aac -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6943984 Update to version 0.20.0; Fixes RHBZ#2259683