Re: [PATCH v1 2/2] add "ok=sigpipe" to test_must_fail and use it to fix flaky tests

[Jeff King <peff@peff.net>]

On Fri, Nov 27, 2015 at 10:15:14AM +0100, larsxschneider@gmail.com wrote:

> From: Lars Schneider <larsxschneider@gmail.com>
> 
> t5516 "75 - deny fetch unreachable SHA1, allowtipsha1inwant=true" is
> flaky in the following case:
> 1. remote upload-pack finds out "not our ref"
> 2. remote sends a response and closes the pipe
> 3. fetch-pack still tries to write commands to the remote upload-pack
> 4. write call in wrapper.c dies with SIGPIPE
> 
> t5504 "9 - push with transfer.fsckobjects" is flaky, too, and returns
> SIGPIPE once in a while. I had to remove the final "To dst..." output
> check because there is no output if the process dies with SIGPUPE.

s/PUPE/PIPE/ :)

I think it would be nice for future readers to understand a bit better
_why_ this is flaky, and why the fix is to the test suite and not to git
itself. I added this paragraph in between the two above:

    The test is flaky because the sending fetch-pack may or may not have
    finished writing its output by step (3). If it did, then we see a
    closed pipe on the next read() call. If it didn't, then we get the
    SIGPIPE from step (4) above. Both are fine, but the latter fools
    test_must_fail.

-Peff