Re: [PATCH] Enable parallelism in git submodule update.

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

Stefan Zager <szager@google.com> writes:

> On Fri, Jul 27, 2012 at 2:38 PM, Junio C Hamano <gitster@pobox.com> wrote:
>
>> Stefan Zager <szager@google.com> writes:
>>
>> > +             module_list "$@" | awk '{print $4}' | xargs -L 1 -P
>> "$jobs" git submodule update $orig_args
>>
>> Capital-P option to xargs is not even in POSIX, no?
>
> I wasn't aware of that, but you appear to be correct.  Don't know if you
> have a policy about that, but anecdotally, -P is supported on my linux,
> mac, and win/msys systems.

About "policy", we use POSIX as a rough yardstick to warn us that we
might be breaking people on minority platforms.  We do _not_ say "It
is in POSIX, so it is safe to use it", but we say "It is not even in
POSIX, so we need to think twice."  We do not usually say "Linux,
Mac and Windows are the only things that matter, and they all
support it."

Of course, any set of rules have exceptions ;-) There are a few
things to which we say "Even though it is not in POSIX, everybody
who matters supports it, and without taking advantage of it, what we
want to achieve will become too cumbersome to express".

In the core parts of the system, we try to be very conservative. In
the fringe where nobody cares about, we tend to be looser.