From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff King Subject: Re: [PATCH 1/2] docs: add a basic description of the config API Date: Tue, 7 Feb 2012 13:06:25 -0500 Message-ID: <20120207180625.GA27189@sigill.intra.peff.net> References: <20120206095306.GA2404@sigill.intra.peff.net> <20120206095346.GA4300@sigill.intra.peff.net> <7vbopb61cd.fsf@alter.siamese.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: git@vger.kernel.org To: Junio C Hamano X-From: git-owner@vger.kernel.org Tue Feb 07 19:06:39 2012 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1RupR6-0003Cp-SQ for gcvg-git-2@plane.gmane.org; Tue, 07 Feb 2012 19:06:37 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756267Ab2BGSG2 (ORCPT ); Tue, 7 Feb 2012 13:06:28 -0500 Received: from 99-108-226-0.lightspeed.iplsin.sbcglobal.net ([99.108.226.0]:59335 "EHLO peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753969Ab2BGSG1 (ORCPT ); Tue, 7 Feb 2012 13:06:27 -0500 Received: (qmail 9578 invoked by uid 107); 7 Feb 2012 18:13:34 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) (smtp-auth username relayok, mechanism cram-md5) by peff.net (qpsmtpd/0.84) with ESMTPA; Tue, 07 Feb 2012 13:13:34 -0500 Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Tue, 07 Feb 2012 13:06:25 -0500 Content-Disposition: inline In-Reply-To: <7vbopb61cd.fsf@alter.siamese.dyndns.org> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Mon, Feb 06, 2012 at 02:31:14PM -0800, Junio C Hamano wrote: > > +Config files are parsed linearly, and each variable found is passed to a > > +caller-provided callback function. The callback function is responsible > > +for any actions to be taken on the config option, and is free to ignore > > +some options (it is not uncommon for the configuration to be parsed > > +several times during the run of a git program, with different callbacks > > +picking out different variables useful to themselves). > > It woud be easeier to read if you stopped the sentence after "some > options" and made the "It is not uncommon..." a first-class sentence > outside the parentheses. Thanks. Putting in too many parenthetical phrases is a bad habit of mine. Usually I notice around the time I try nesting a parenthetical phrase instead of existing parentheses, and go back and at least promote the outer one to a real sentence. :) Will fix for the re-roll. > > +A config callback should return 0 for success, or -1 if the variable > > +could not be parsed properly. > > This matches what I have always thought, but I think I recently saw a > series that adds callbacks that return 1 to mean "I have understood this > variable, so callers should not look at it any more". It felt wrong, but > I did not find anything in the config.c API framework to prvent such a > local calling convention. The return value is propagated from git_parse_file. I assume the original intent was that you could actually use it to return an integer from your callback. In practice, though, callbacks either modify global data (for older instances), or modify a pointer passed through the void data pointer. The "1 means I understood this" convention is used by userdiff_config. I don't like that it is unlike every other config callback, but I think it's necessary to deal with the ambiguity of "diff.color.*", which could be either a userdiff entry or a diff color. E.g., if we see "diff.color.binary", we know that it is the "binary" variable of the "color" diff driver, not the color spec for the "binary" slot. Looking at the code again, though, it seems that there is no overlap between the userdiff slots and the color slots, and that the color-parsing code will silently ignore any unknown slots. So it would be safe to further investigate diff.color.binary as a color, as we would silently ignore it. Hmm. Yeah. The userdiff calling convention dates back to late 2008. At that time, parse_diff_color_slot would die() if it did not understand the slot, making the "I understood this" flag required. Then later, in 8b8e862 (ignore unknown color configuration, 2009-12-12), it was relaxed. So I think we could go back and simplify the userdiff_config code now. > > +There is a special version of `git_config` called `git_config_early` > > +that takes an additional parameter to specify the repository config. > > +This should be used early in a git program when the repository location > > +has not yet been determined (and calling the usual lazy-evaluation > > +lookup rules would yield an incorrect location). > > Do you want to say somethink like "Ordinary programs should not have to > worry about git_config_early()"? Differently put, if you are learning the > config API by reading this document and cannot tell which one you should > be calling, you are way too inexperienced to call git_config_early() and > you would always want to call git_config()? Yes, I think that would be sensible. Though having looked a lot at the config code recently, I wonder if git_config_early is really necessary. The only caller (besides git_config) is check_repository_format_early, which just wants to see if core.repositoryformatversion in a directory is sane. But why in the world would it want to do the full config lookup? Shouldn't it be checking git_config_from_file directly on the config file in the proposed repo? -Peff