Re: PATCH: revert 39611 and add tests and comments

[Bart Schaefer <schaefer@brasslantern.com>]

On Dec 8,  9:04pm, Oliver Kiddle wrote:
}
} In an attempt to avoid a repeat when I come to do that, this adds
} fairly comprehensive tests of _arguments. No tests for the little
} used -w because it is either broken or I was too confused. Or -n
} for somewhat similar reasons.  A few tests are commented where I
} think the behaviour is not right.

I've been adding such comments as "F:" lines in the redirection part
of the test, so that they're printed if the test fails.  Comment in
B01cd says "useful for explaining certain frequent errors, for example
ones which may arise from the environment rather than from the shell"
but this seems ideal for explaining *expected* failures such as might
happen if a questionable behavior is deliberately changed.