$ git clone -n https://src.fedoraproject.org/rpms/rust-thiserror.git /var/lib/mock/f40-build-2478157-61606/root/chroot_tmpdir/scmroot/rust-thiserror
Cloning into '/var/lib/mock/f40-build-2478157-61606/root/chroot_tmpdir/scmroot/rust-thiserror'...
$ git fetch origin 8fb84b1fb38810f4f9bf1a8f2048838a06da1c86:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-thiserror
 * [new ref]         8fb84b1fb38810f4f9bf1a8f2048838a06da1c86 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8fb84b1 Update to version 1.0.57; Fixes RHBZ#2263774