produces output with a very large number of consecutive embegged \n
characters.
This test is currently expected to fail (as of commit date) but is not
marked as atf_expect_fail as the shell should be fixed to avoid the
problem quite soon. Until then almost anything might happen to the
sh that runs this test (from just plain wrong results, to core dumps,
even possibly the right results, though that's unlikely).
Whie doing this, get rid of the duplicate implementation of the
nested_cmdsubs_in_heredoc test (which was achieving nothing). I know
how I managed to do that, but on advice of counsel, I ... (it was
just a harmless waste of a tiny amount of CPU time "compiling" the test,
just like writing "x=0;" on consecutive lines....)