$ git clone -n https://src.fedoraproject.org/rpms/rust-serde_derive.git /var/lib/mock/f39-build-2196391-51569/root/chroot_tmpdir/scmroot/rust-serde_derive
Cloning into '/var/lib/mock/f39-build-2196391-51569/root/chroot_tmpdir/scmroot/rust-serde_derive'...
$ git fetch origin 00eae69f1aefb8ed6d9228d9a99be2492fe8927e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-serde_derive
 * [new ref]         00eae69f1aefb8ed6d9228d9a99be2492fe8927e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 00eae69 Update to version 1.0.194; Fixes RHBZ#2256428