$ git clone -n https://src.fedoraproject.org/rpms/thunderbird.git /var/lib/mock/f39-build-1955809-43240/root/chroot_tmpdir/scmroot/thunderbird
Cloning into '/var/lib/mock/f39-build-1955809-43240/root/chroot_tmpdir/scmroot/thunderbird'...
$ git fetch origin 9de489d34cddc1567f1c8067f5ba87d85b26abdf:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/thunderbird
 * [new ref]         9de489d34cddc1567f1c8067f5ba87d85b26abdf -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9de489d Update to 115.5.1