Subject: Re: [RFC PATCH 0/2] Conditional config includes based on remote URL

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Tue, 26 Oct 2021 12:12:12 +0200

On Mon, Oct 25 2021, Jonathan Tan wrote:

>> I had some concerns about the specifics of the implementation/what
>> seemed to be tailoring it a bit too closely to one use-case[1][2], not
>> inherently with the idea (although I think e.g. for brian that more
>> closely reflects his thoughts).
>> 
>> Anyway, just saying that aside from this RFC I don't think we were at
>> the point of really fleshing out what this would look like, and there
>> being some hard "no", so I think that idea could still be pursued.
>
> Which idea specifically do you think could still be pursued?

I meant the whole in-repo .gitconfig. I.e. to the extent that you're
submitting this as an alternative to that because of the negative
feedback on that RFC.

>> On this proposal: this also applies globally to all history, but I don't
>> have the same concern with that as the 1=1 mapping of remote-suggested
>> hooks, our path includes work that way, after all.
>> 
>> I think it would be nice if you could think about if/how this and the
>> "onbranch" include would work together though to serve the general case
>> better.
>> 
>> Also if you have a repo with N remotes each where "origin" tracks URLs
>> at git.example.com, and you add a "dev" tracking dev.example.com, will
>> the config apply if you're say on a branch tracking the "live" server,
>> if you've said "include this for repos matching dev.example.com?
>
> Right now, the feature is only dependent on remote URLs configured
> through remote.?.url. It wouldn't work with "onbranch" because there's
> no way to combine conditions (and I have no plans to do that). I think
> that if you have something that you want depending on which branch
> you're on, you can just use the existing "onbranch" feature.

I mean with this and the below...

>> Arguably that's what you want, but perhaps something that those more
>> used to the centralized workflows wouldn't consider as being unintuitive
>> for users who might want to add this config only for their main "origin"
>> remote. We don't really have a way of marking that special-ness though,
>> except maybe checkout.defaultRemote.
>
> What do you mean by adding a config for a specific remote?

...what happens if you add a google.com remote for a repository that
"lives" on github.com. I.e. are the semantics "match any remote", or
"match the 'primary' remote (origin?" etc.

>> I'm also still somewhat mystified at how this would better serve your
>> userbase than the path-based included, i.e. the selling point of the
>> remote-suggested configuration was that it would Just Work.
>> 
>> But for this the users would either need to setup the config themselves
>> for your remote, but that would be easier than pro-actively cloning in
>> "work" or whatever? I guess, just wondering if I'm missing something.
>> 
>> Or if it's a partly-automated system where some automation is dropping
>> in a /etc/gitconfig.d/google-remote-config-include 
>
> Yes, the config is meant to be handled e.g. through a package manager
> like apt. We don't want to prescribe directory structures like "work",
> which is why the include is conditional upon the remote URL.
>
> Even if the user pro-actively clones into "work", the user still needs
> to set up the conditional config, so I don't see how that is a net
> benefit.

Ah, that explains it. I assumed both cases would be ones where the user
would need to manually enable the 'configuration' (or cloning to a given
subdir).

>> I wonder if this
>> whole thing wouldn't be better for users with such special-needs if we
>> just supported an "early config hook".
>> 
>> i.e. similar to how we read trace2 config from /etc/gitconfig early, we
>> could start picking up a hook that just so happens to conform to the
>> config schema Emily's config-based hooks use.
>> 
>> So the /etc/gitconfig would have say:
>> 
>>     hook.ourConfigThingy.command=/usr/bin/googly-git-config
>>     hook.ourConfigThingy.event=include-config
>> 
>> That hook would just produce a config snippet to be included on STDOUT.
>> 
>> Since it's an arbitrary external command it would nicely get around any
>> chicken and egg problems in git itself, it could run "git remote -v",
>> inspect the equivalent of an "onbranch" etc. etc, then just dynamically
>> produce config-to-be-included.
>
> I see that later on, you suggest an environment variable to guard
> against recursion.
>
> One thing is that if there are multiple such hooks, each one won't be
> able to see what the other hooks have produced.

Yes, although aside from this hook that's a general caveat with the
proposed config-based hooks, I think if you need a hook that does that
(whether it's this, or pre-receive etc.) our answer is "put it in your
own wrapper".

> If the feature you described already existed in Git, I think I could use
> that, but if we're deciding between implementing the config hook you
> describe versus something with more constraints, I think the one I
> proposed is better for now. Some design points that have already been
> discussed are whether setting a config during processing of an included
> file would then invalidate the include and also the order of operations,
> both of which would be much more difficult to control with config hooks.

I suggested it because maybe it would be a lot simpler, i.e. we don't
need such a feature to be aware of remote config at all, or having to
"read forward" to find it, maybe it would be more complex. I haven't
tried to implement it.

>> Please don't take this as some objection to your current proposal, just
>> a thought on something that might entirely bypass odd edge cases and
>> arbitrary limitations associated with doing this all in the "main"
>> process on-the-fly.
>> 
>> The special-ness with that one would need to be that we'd say it
>> wouldn't have the normal "last set wins" semantics, or maybe we could do
>> that and just note that we saw it, and execute the "include" when we
>> detect the end of the full config parsing (I'm not familiar enough with
>> those bits to say where that is).
>
> The "last set" would be those set by the hooks, so yes, a user would
> need to know to make their own hook in order to override anything set by
> the hooks. The end of the full config parsing is in
> config_with_options().

On the "user would need to know" that's the same if it's config? I.e. in
either case it would be in /etc/gitconfig or whatever shipped by the
*.deb package.

Anyway, I really just meant this as a suggestion, and one that might
make things simpler. If you don't think it makes sense...