$ git clone -n https://src.fedoraproject.org/rpms/mumble.git /var/lib/mock/f39-build-1628923-39492/root/chroot_tmpdir/scmroot/mumble
Cloning into '/var/lib/mock/f39-build-1628923-39492/root/chroot_tmpdir/scmroot/mumble'...
$ git fetch origin a4abd0505011b92dfc9fc7d0bb397304b71c484d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mumble
 * [new ref]         a4abd0505011b92dfc9fc7d0bb397304b71c484d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a4abd05 Update to version 1.4.287, resolves rhbz#2126913