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

From: John Keeping <john@keeping.me.uk>
Date: Jun 9, 2013, 17:32 UTC
Message-ID: <20130609173257.GE22905@serenity.lan>
In-Reply-To: <CAMP44s1PENiKMy03_mgZ_myiGP5+qpaE2bvo0LN3X3mZhSvT2g@mail.gmail.com>

On Sun, Jun 09, 2013 at 12:13:41PM -0500, Felipe Contreras wrote:

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> On Sun, Jun 9, 2013 at 12:03 PM, Ramkumar Ramachandra
> <artagnon@gmail.com> wrote:
> > John Keeping wrote:
> >> Calling across from one builtin/*.c file to another is just as wrong as
> >> calling into a builtin/*.c file from a top-level file but the build
> >> system happens not to enforce the former.
> >
> > So libgit.a is a collection of everything that is shared between
> > builtins?  Does that correspond to reality?

I think that's *precisely* what libgit.a is. It doesn't currently correspond exactly to reality, but that's mostly for historic reasons (see below).

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> >   $ ls *.h | sed 's/.h$/.c/' | xargs file
> >
> > An example violation: builtin/log.c uses functions defined in
> > builtin/shortlog.c.
> >
> > What is the point of all this separation, if no external scripts are
> > ever going to use libgit.a?

Why do we structure code in a certain way at all? The reason libgit.a was introduced (according to commit 0a02ce7) is:

    This introduces the concept of git "library" objects that
    the real programs use, and makes it easier to add such
    things to a "libgit.a".

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> And all the functions should be static, which doesn't seem to be the case:
> 
> 00000000000003c0 T add_files_to_cache
> 0000000000000530 T interactive_add
> 0000000000000410 T run_add_interactive
> 0000000000001920 T textconv_object
> 00000000000005b0 T fmt_merge_msg
> 0000000000000090 T fmt_merge_msg_config
> 0000000000000c00 T init_db
> 0000000000000b40 T set_git_dir_init
> 0000000000000360 T overlay_tree_on_cache
> 0000000000000500 T report_path_error
> 00000000000011a0 T copy_note_for_rewrite
> 0000000000001210 T finish_copy_notes_for_rewrite
> 0000000000001060 T init_copy_notes_for_rewrite
> 0000000000000000 T prune_packed_objects
> 0000000000000510 T shortlog_add_commit
> 00000000000006b0 T shortlog_init
> 0000000000000780 T shortlog_output
> 0000000000000000 T stripspace

A quick check with "git log -S..." shows that most of these have barely been touched since the builtin/ directory was created. So the reason they're not static is most likely because no one has tidied them up since the division between builtins was introduced.

It is a fact of life that as we live and work with a system we realise that there may be a better way of doing something. This doesn't mean that someone needs to immediately convert everything to the new way, it is often sufficient to do new things in the new way and slowly move existing things across as and when they are touched for other reasons.