Subject: Re: [PATCH 2/2] config: allow specifying config entries via envvar pairs

From: Patrick Steinhardt <[email-masked]>
Date: Wed, 18 Nov 2020 08:04:30 +0100

On Wed, Nov 18, 2020 at 02:25:32AM +0000, brian m. carlson wrote:
> On 2020-11-18 at 01:59:07, Jeff King wrote:
> > Yes, I think concatenating uri_encode(key) + "=" + uri_encode(value)
> > would be easier to reason about, and solves the ambiguity problem. If we
> > are willing to break from the existing format, it's probably a
> > reasonable direction.
> 
> We'll have to deal with embedded NULs, but other than that it seems
> robust and easy to reason about.  I like the proposal below better,
> though.

This would be easy enough to handle and fixes all the problems I
currently have.

> > I wondered at first how this is different from:
> > 
> >   git -c a.b.c=value foo
> > 
> > but I guess it is meant to do the same environment-lookup? We could
> > probably add:
> > 
> >   git --env-config a.b.c=ENV_VAR foo
> > 
> > to have Git internally stick $ENV_VAR into $GIT_CONFIG_PARAMETERS. That
> > avoids all of the rev-parse rigamarole, keeps the format of the
> > environment variable opaque, and solves Patrick's problem of putting the
> > value onto the command-line.
> 
> Sure, that could be an option.  It's the simplest, and we already know
> how to handle config this way.  People will be able to figure out how to
> use it pretty easily.

At first, this idea sounds quite interesting. But only until one
realizes that it's got the exact same problem which I'm trying to solve:
there's still a point in time where one can observe config values via
the command line, even though that moment now is a lot shorter compared
to running the "real" git command with those keys.

> > It doesn't solve the ambiguity with "=" in the subsection, but IMHO that
> > is not all that important a problem.
> 
> I'm fine with saying that we don't support environment variable names
> with equals signs and just going with that.  It solves the ambiguity
> problem and I'm not sure that they could usefully work on Unix anyway.
> 
> Moreover, people usually use the unrestricted data in the second chunk
> for URLs, which shouldn't have unquoted equals signs.  You could
> technically name other second fields that way, but why would you when
> you could just not?
> 
> So I'm not too worried about it either way.

There's not only URLs though, but also paths in 'includeIf.*.path'.
Sure, it's unlikely that paths have an equals sign embedded. But I think
we should try to not paint ourselves into a corner.

This problem also would be nicely solved by URI-encoding both key and
value and then passing it via GIT_CONFIG_PARAMETER.

Patrick