$ git clone -n https://src.fedoraproject.org/rpms/rust-base64_0.12.git /var/lib/mock/f39-build-1499509-34745/root/chroot_tmpdir/scmroot/rust-base64_0.12
Cloning into '/var/lib/mock/f39-build-1499509-34745/root/chroot_tmpdir/scmroot/rust-base64_0.12'...
$ git fetch origin 73a1616942eb4385b02ba027a165b428dfb2c833:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-base64_0.12
 * [new ref]         73a1616942eb4385b02ba027a165b428dfb2c833 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 73a1616 Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild