Re: [PATCH 2/3] t: teach 'test_must_fail' to save the command's stderr to a file

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

>   2. The "-x" problems aren't specific to test_must_fail at all. They're
>      a general issue with shell functions.
>
> I'm not entirely happy with saying "if you want to use -x, please use
> bash". But given that it actually solves the problems everywhere with no
> further effort, is it really that bad a solution?
>
> For the error messages from test_must_fail, could we go in the same
> direction, and send them to descriptor 4 rather than 2? We've already
> staked out descriptor 4 as something magical that must be left alone
> (see 9be795fb). If we can rely on that, then it becomes a convenient way
> for functions to make sure their output is going to the script's stderr.

That sounds clever and rather attractive.  It isn't that much of an
layering violation for test-lib-functions.sh::test_must_fail to have
such an intimate knowledge on how test_-lib.sh::test_eval_ sets up
the file descriptors, either.