$ git clone -n https://src.fedoraproject.org/rpms/rust-thiserror.git /var/lib/mock/f38-build-side-43-rust-devel-1417914-31459/root/chroot_tmpdir/scmroot/rust-thiserror
Cloning into '/var/lib/mock/f38-build-side-43-rust-devel-1417914-31459/root/chroot_tmpdir/scmroot/rust-thiserror'...
$ git fetch origin e8ea57c4b0f54a255432bba28fa9e9febd51698c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-thiserror
 * [new ref]         e8ea57c4b0f54a255432bba28fa9e9febd51698c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e8ea57c Update to version 1.0.49; Fixes RHBZ#2240866