Some git-merge-* commands are not merge strategies. This is based on
v1.6.1-rc1~294^2~7 (builtin-merge: allow using a custom strategy,
2008-07-30) but it is less smart: we just use a hard-coded list of
forbidden strategy names. It is okay if this falls out of date, since
the code is just an example.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>