$ git clone -n https://src.fedoraproject.org/rpms/libgit2.git /var/lib/mock/f41-build-847428-163983/root/chroot_tmpdir/scmroot/libgit2
Cloning into '/var/lib/mock/f41-build-847428-163983/root/chroot_tmpdir/scmroot/libgit2'...
$ git fetch origin 7fa50c0767e37ec1289cda341f7adc4f9ec04ff7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libgit2
 * [new ref]         7fa50c0767e37ec1289cda341f7adc4f9ec04ff7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7fa50c0 Update to 1.8.1 (rhbz#2270542)