$ git clone -n https://src.fedoraproject.org/rpms/jgit.git /var/lib/mock/f41-build-1283376-23209/root/chroot_tmpdir/scmroot/jgit
Cloning into '/var/lib/mock/f41-build-1283376-23209/root/chroot_tmpdir/scmroot/jgit'...
$ git fetch origin 55123002a228cb496a1b523d716d61b7acaf8c1a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jgit
 * [new ref]         55123002a228cb496a1b523d716d61b7acaf8c1a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5512300 Eliminate use of obsolete %patchN syntax (#2283636)