t1200: prepare for merging with Fast-forward bikeshedding

t1200: prepare for merging with Fast-forward bikeshedding

A tree-wide bikeshedding to replace "fast forward" into "fast-forward" is
in 'master'.  Since we want to keep this "test modernization" series
mergeable also to the maintenance track, we would need to tweak the test
to accept both old spellings and new spellings.

Sigh...  This kind of headache is the primary reason we try not to allow
such a tree-wide bike-shedding, but the damage has already been done.

Signed-off-by: Junio C Hamano <gitster@pobox.com>