$ git clone -n https://src.fedoraproject.org/rpms/aerc.git /var/lib/mock/f41-build-851883-166121/root/chroot_tmpdir/scmroot/aerc
Cloning into '/var/lib/mock/f41-build-851883-166121/root/chroot_tmpdir/scmroot/aerc'...
$ git fetch origin 2ba4d2219d4f51008371ea91b9c05cfde6245c0d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/aerc
 * [new ref]         2ba4d2219d4f51008371ea91b9c05cfde6245c0d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2ba4d22 Update to 0.18.2.