Re: sub-fetches discard --ipv4|6 option

From: Alex Riesen <alexander.riesen@cetitec.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Eric Wong <normalperson@yhbt.net>,
	Junio C Hamano <gitster@pobox.com>
Subject: Re: sub-fetches discard --ipv4|6 option
Date: Thu, 17 Sep 2020 16:33:39 +0200	[thread overview]
Message-ID: <20200917143339.GF8079@pflmari> (raw)
In-Reply-To: <20200916163218.GA17726@coredump.intra.peff.net>

Jeff King, Wed, Sep 16, 2020 18:32:18 +0200:
> On Tue, Sep 15, 2020 at 06:03:57PM +0200, Alex Riesen wrote:
> 
> > > If you go that route, we have some "_F" macros that take flags. Probably
> > > would make sense to add it more consistently, which lets you convert:
> > > 
> > >   OPT_BOOL('f', "foo", &foo, "the foo option");
> > > 
> > > into:
> > > 
> > >   OPT_BOOL_F('f', "foo", &foo, "the foo option", PARSE_OPT_RECURSIVE);
> > > 
> > > but could also be used for other flags.
> > 
> > This part (marking of the options) was easy. What's left is finding out if an
> > option was actually specified in the command-line. The ...options[] arrays are
> > not update by parse_options() with what was given, are they?
> 
> Oh right. Having the list of options is not that helpful because
> add_options_argv() is actually working off the parsed data in individual
> variables. Sorry for leading you in a (maybe) wrong direction.
...
> > Or is it possible to use something in parse-options.h API to note the
> > arguments somewhere while they are parsed? I mean, there are
> > parse_options_start/step/end, can cmd_fetch argument parsing use those
> > so that the options marked recursive can be saved for sub-fetches?
> 
> Possibly the step-wise parsing could help. But I think it might be
> easier to just let parse_options() save a copy of parsed options. And
> then our PARSE_OPT_RECURSIVE really becomes PARSE_OPT_SAVE or similar,
> which would cause parse-options to save the original option (and any
> value argument) in its original form.
> 
> There's one slight complication, which is how the array of saved options
> gets communicated back to the caller. Leaving them in the original argv
> probably isn't a good idea (because the caller relies on it having
> options removed in order to find the non-option arguments).
> 
> Adding a new strvec pointer to parse_options() works, but means updating
> all of the callers, most of which will pass NULL. Possibly the existing
> "flags" parameter to parse_options() could grow into a struct. That
> requires modifying each caller, but at least solves the problem once and
> for all.

With such complication a step-wise parsing sounds easier, given that at the
moment there is only one user for the feature. Are there *existing* callers
of parse_options with similar requirements?

I feel that doing this kind of selection work in parse_options is an overkill:
if it is specific for just this use case, the implementation might be more
complex than necessary, while profiting just one caller.

> Another option is to stick it into parse_opt_ctx_t. That's used only be
> step-wise callers, of which there are very few.

Does that mean that currently there is no way to find out which option
corresponds to the last parsed command-line argument after a call to
parse_options_step? Which in turn makes the marking of recursive options
inaccessible to step-wise command line parsing code, right?