Re: [PATCH] build: get rid of the notion of a git library

From: Felipe Contreras <felipe.contreras@gmail.com>
Date: Jun 11, 2013, 19:01 UTC
Message-ID: <CAMP44s3SL7qs-Pmfz=kV-4U5OnPedK2RDLZDOyU-eq8WebLt+Q@mail.gmail.com>
In-Reply-To: <7vd2rsbjgr.fsf@alter.siamese.dyndns.org>

On Tue, Jun 11, 2013 at 1:17 PM, Junio C Hamano <gitster@pobox.com> wrote:

Show 9 quoted lines

> Felipe Contreras <felipe.contreras@gmail.com> writes:
>
>> Moreover, if you are going to argue that we shouldn't be closing the
>> door, then why not link ./builtin/*.o to libgit.a?
>
> Huh?  It does not make any sense.  builtin/*.o files have cmd_foo()
> that are expected to be called from git.c::main(), but libgit.a
> files are linked with no constraints whose main() they are linking
> with.

Show 15 quoted lines

>> If you are
>> seriously considering the highly unlikely hypothetical standalone
>> git-filter-branch scenario, you should consider the even more likely
>> scenario where somebody needs to access code from ./builtin/*.o; that
>> scenario is not even hypothetical, we know it's happened multiple
>> times, and we know it's going to happen again.
>
> That is exactly why I said that builtin/*.o should be refactored to
> pick "does not have to be in builtin" bits, which will result in a
> better division of labor.  Reusable bits should live in the library,
> while a particular implementation of command remain in builtin/*
> that utilize the reusable bits.
>
> You still haven't justified why we have to _forbid_ any outside
> callers from calling copy_notes_for_rewrite().

Because only builtins _should_ use it. I asked you for an example, and you said a hypothetical standalone 'git-filter-branch' might use it, but you have not explained why it should be standalone, when it's clear it should be a builtin.

If we assume your argument is valid for the hypothetical 'git-filter-branch', if that's the case, then it would be even more reasonable to assume that there will be other standalone binaries that would want to use all sort of functions from ./builtin/*.o. Let's put an example: reset_index(). Some standalone program wants to use that function. What do you we do?

The shortest route is to make it non-static, and add it to builtin.h. But that would not be enough, we need the infrastructure prepared for that; link libgit.a with ./builtin/*.o.

I don't think that's the way to go, but your line of argumentation leads directly there; if we are worrying about anything that any potential standalone program could want, then we should worry about reset_index() not being easily accessible to them.

IMO we should be clear and say no; standalone programs should not access copy_notes_for_rewrite(), that's for builtins. If we move all the code that potential standalone programs could want to libgit.a, it wouldn't be a library at all, and it would basically contain everything.

-- 
Felipe Contreras