$ git clone -n https://src.fedoraproject.org/rpms/rust-num-bigint.git /var/lib/mock/f40-build-1194335-22252/root/chroot_tmpdir/scmroot/rust-num-bigint
Cloning into '/var/lib/mock/f40-build-1194335-22252/root/chroot_tmpdir/scmroot/rust-num-bigint'...
$ git fetch origin 3765fcfb6b207db20290cdcdb369f877bffecb7a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-num-bigint
 * [new ref]         3765fcfb6b207db20290cdcdb369f877bffecb7a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3765fcf Update to version 0.4.5; Fixes RHBZ#2279412