$ git clone -n https://src.fedoraproject.org/rpms/libgit2.git /var/lib/mock/f40-build-2007367-45253/root/chroot_tmpdir/scmroot/libgit2
Cloning into '/var/lib/mock/f40-build-2007367-45253/root/chroot_tmpdir/scmroot/libgit2'...
$ git fetch origin 26de4b0cba47571f39be64191030991de5d77234:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libgit2
 * [new ref]         26de4b0cba47571f39be64191030991de5d77234 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 26de4b0 Use krb5 GSSAPI