Re: [PATCH v3 2/3] git-push: clean up some of the output from git push --porcelain

From: Jeff King <peff@peff.net>
Date: Feb 10, 2010, 05:39 UTC
Message-ID: <20100210053937.GF28526@coredump.intra.peff.net>
In-Reply-To: <7viqa7cqs9.fsf@alter.siamese.dyndns.org>

On Mon, Feb 08, 2010 at 02:21:26PM -0800, Junio C Hamano wrote:

> I think the purpose of the patches that started this thread was to admit
> that 1965ff7 (add --porcelain option to git-push, 2009-06-22) was not well
> thought out, and to break compatibility to fix it.

I thought it was simply to remove stdout cruft that had crept in, and at the same time to remove some stderr cruft that was simply noise on the terminal. That being said, I am in favor of fixing it even if it means a slight compatibility breakage.

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> Having said that, I would say that what 1965ff7 specified was only these
> two:
> 
>     = TAB refs/heads/master:refs/heads/master TAB [up to date]
>     - TAB :refs/heads/foobar TAB [deleted]
> 
> so everything else that do not match this pattern is a fair game, most
> importantly, the line that begins with "To" would not be mistaken with
> this pattern, I think.

It depends on the parser. If the parser was something like:

  switch (line[0]) {
    case '=': ...; break;
    case '-': ...; break;
    default: die("wtf: %s", line);
  }

then we are not introducing any ambiguity, but we are causing a breakage. The problem is that we did not specify the format anywhere, so it is hard to say whether we are breaking any promises we made.

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> > This one, on the other hand, seems to me to be just noise. What does a
> > --porcelain caller learn by seeing "Everything up-to-date" that it did
> > not already know from seeing the list of refs?
> 
> I do not care too much about this hunk either way.  We could leave it as
> is, as we will be giving some other stuff to the standard error stream
> without squelching anyway, even with the three-patch series.  We could
> squelch only this message, but it is dubious what it is buying us.  If you
> forced me to decide, I would probably say "let's just drop this hunk and
> keep the code as-is".

I have not actually been running these patches, just reading them, but my impression was the goal _was_ to squelch all of the stderr cruft. But if we are not even close, then probably we should just give up and callers should "2>/dev/null".

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> As to the exit status, do you have any thoughts, by the way?
> 
> I am not convinced that it would be necessary nor even a good idea to make
> it behave inconsistently between the normal case and Porcelain case, only
> to make it easier to special case the "remote side would reject due to
> non-fast-forward" failure mode (iow, even if the calling script knows that
> it would fail due to non-fast-forward but otherwise everything else would
> be fine, what good would it do?)

I had initially endorsed it, but now I am having second thoughts. Especially if the "usual" calling convention is to redirect stderr as above, then we are probably missing out on any useful error messages that accompany a failure return, anyway. So maybe the sane thing to do is to leave the exit code alone, and include a --porcelain output line that either says "Everything was OK, see individual ref status" or "We couldn't even talk to the other side". Then the status code is irrelevant, and stdout contains all of the useful information (and if you don't get an error or OK message, you know there was some serious error like a broken git installation).

-Peff