t3404: relax rebase.missingCommitsCheck tests
These tests were a bit anal about the *exact* warning/error message
printed by git rebase. But those messages are intended for the *end
user*, therefore it does not make sense to test so rigidly for the
*exact* wording.
In the following, we will reimplement the missing commits check in
the sequencer, with slightly different words.
So let's just test for the parts in the warning/error message that
we *really* care about, nothing more, nothing less.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>