$ git clone -n https://src.fedoraproject.org/rpms/rust-typed-arena1.git /var/lib/mock/f42-build-3251779-41222/root/chroot_tmpdir/scmroot/rust-typed-arena1
Cloning into '/var/lib/mock/f42-build-3251779-41222/root/chroot_tmpdir/scmroot/rust-typed-arena1'...
$ git fetch origin 6e8870890fe84f8df7696c22b0aa5a57e90ead9f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-typed-arena1
 * [new ref]         6e8870890fe84f8df7696c22b0aa5a57e90ead9f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6e88708 compat package no longer needed