Re: What's cooking in git.git (Apr 2019, #01; Thu, 4)

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

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

> unique (AFAICT "actually unique" in practice) in the parallel in-flight
> jh/trace2-sid-fix
> (https://public-inbox.org/git/4352952677a11776a18ec9b6862cf358307cfafd.1553879063.git.gitgitgadget@gmail.com/)
>
> I think it's fine to merge js/trace2-to-directory down as it is, but do
> you/Josh think that retry logic needs to stay with that sort of SID?

I do not speak for Josh, but I think the only two logical choices
are to open with (O_CREAT|O_EXCL) and

 (1) fallback with .%d suffix, making it clear that we are not
     willing to lose log files even when SID generation is botched; or

 (2) die/BUG when it fails, making it clear that we do rely on the
     guanateed uniqueness of SID.

A distant third may be to warn when open with O_CREAT|O_EXCL fails,
but I am not sure what its value would be to do so---especially if
we trust in the "actually unique in practice".  Between (1) and (2),
I have a slight preference to (1) over (2), as that is much easier
to explain.

Those who want to have a "fixed width" thing could just ignore the
ones with suffix---as long as the "actually unique in practice"
claim holds, doing so will not lose any non-negligible amount of
information anyway.