$ git clone -n https://src.fedoraproject.org/rpms/libgit2.git /var/lib/mock/f42-build-865313-172983/root/chroot_tmpdir/scmroot/libgit2
Cloning into '/var/lib/mock/f42-build-865313-172983/root/chroot_tmpdir/scmroot/libgit2'...
$ git fetch origin fa8d567b1d7fc218c216dd98a443edef165e6b93:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libgit2
 * [new ref]         fa8d567b1d7fc218c216dd98a443edef165e6b93 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fa8d567 Update to 1.8.4