Re: The config include mechanism doesn't allow for overwriting

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Oct 23, 2012, 14:13 UTC
Message-ID: <CACBZZX5mOb7_i9r8AqNK5V3r-gVnzN+rkeY9xrhecGv1rS-anA@mail.gmail.com>
In-Reply-To: <20121022211505.GA3301@sigill.intra.peff.net>

On Mon, Oct 22, 2012 at 11:15 PM, Jeff King <peff@peff.net> wrote:

Show 51 quoted lines

> On Mon, Oct 22, 2012 at 05:55:00PM +0200, Ævar Arnfjörð Bjarmason wrote:
>
>> I was hoping to write something like this:
>>
>>     [user]
>>         name = Luser
>>         email = some-default@example.com
>>     [include]
>>         path = ~/.gitconfig.d/user-email
>>
>> Where that file would contain:
>>
>>     [user]
>>         email = local-email@example.com
>
> The intent is that it would work as you expect, and produce
> local-email@example.com.
>
>> But when you do that git prints:
>>
>>     $ git config --get user.email
>>      some-default@example.com
>>      error: More than one value for the key user.email: local-email@example.com
>
> Ugh. The config code just feeds all the values sequentially to the
> callback. The normal callbacks within git will overwrite old values,
> whether from earlier in the file, from a file with lower priority (e.g.,
> /etc/gitconfig versus ~/.gitconfig), or from an earlier included. Which
> you can check with:
>
>   $ git var GIT_AUTHOR_IDENT
>   Luser <local-email@example.com> 1350936694 -0400
>
> But git-config takes it upon itself to detect duplicates in its
> callback. Which is just silly, since it is not something that regular
> git would do. git-config should behave as much like the internal git
> parser as possible.
>
>> I think config inclusion is much less useful when you can't clobber
>> previously assigned values.
>
> Agreed. But I think the bug is in git-config, not in the include
> mechanism. I think I'd like to do something like the patch below, which
> just reuses the regular config code for git-config, collects the values,
> and then reports them. It does mean we use a little more memory (for the
> sake of simplicity, we store values instead of streaming them out), but
> the code is much shorter, less confusing, and automatically matches what
> regular git_config() does.
>
> It fails a few tests in t1300, but it looks like those tests are testing
> for the behavior we have identified as wrong, and should be fixed.

I think this patch looks good.

One other thing I think is worth clarifying (and I think should be broken) is if you write a configuration like:

    [foo]
        bar = one
    [foo]
        bar = two
    [foo]
        bar = three

"git-{config,var} -l" will both give you:

    foo.bar=one
    foo.bar=two
    foo.bar=three

And git config --get foo.bar will give you:

    $ git config -f /tmp/test --get foo.bar
    one
    error: More than one value for the key foo.bar: two
    error: More than one value for the key foo.bar: three

I think that it would be better if the config mechanism just silently overwrote keys that clobbered earlier keys like your patch does.

But in addition can we simplify things for the consumers of "git-{config,var} -l" by only printing:

    foo.bar=three

Or are there too many variables like "include.path" that can legitimately appear more than once.