Subject: Re: [PATCH v2 1/3] repo-settings: create core.featureAdoptionRate setting

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Tue, 02 Jul 2019 12:47:15 +0200

On Wed, Jun 19 2019, Derrick Stolee via GitGitGadget wrote:

>  core.commitGraph::
>  	If true, then git will read the commit-graph file (if it exists)
> -	to parse the graph structure of commits. Defaults to false. See
> +	to parse the graph structure of commits. Defaults to false, unless
> +	`core.featureAdoptionRate` is at least three. See
>  	linkgit:git-commit-graph[1] for more information.
>
>  core.useReplaceRefs::
> @@ -601,3 +602,21 @@ core.abbrev::
>  	in your repository, which hopefully is enough for
>  	abbreviated object names to stay unique for some time.
>  	The minimum length is 4.
> +
> +core.featureAdoptionRate::
> +	Set an integer value on a scale from 0 to 10 describing your
> +	desire to adopt new performance features. Defaults to 0. As
> +	the value increases, features are enabled by changing the
> +	default values of other config settings. If a config variable
> +	is specified explicitly, the explicit value will override these
> +	defaults:
> ++
> +If the value is at least 3, then the following defaults are modified.
> +These represent relatively new features that have existed for multiple
> +major releases, and present significant performance benefits. They do
> +not modify the user-facing output of porcelain commands.
> ++
> +* `core.commitGraph=true` enables reading commit-graph files.
> ++
> +* `gc.writeCommitGraph=true` eneables writing commit-graph files during

I barked up a similar tree in
https://public-inbox.org/git/[email-masked]/

I wonder if you've seen that & what you think about that
approach. I.e. have a core.version=2.28 (or core.version=+6) or whatever
to opt-in to features we'd make default in 2.28. Would that be your
core.featureAdoptionRate=6 (28-28 = 6)?

I admit that question is partly rhetorical, because I think it suggests
how hard it would be for users to reason about this.

The "core.version" idea also sucks, but at least it's bound to our
advertised version number, so it's obvious if you set it to e.g. +2 what
feature track you're on, and furthermore when we'd commit to making that
the default for users who don't set core.version (although we could of
course always change our minds...). It's also something that mirrors how
e.g. Perl, C compilers (with --std=*) treat this sort of thing.

So I'm all for a facility to have a setting to collectively opt-in to
new things early. But I think for such a thing we really should a) at
least in principle commit to making those things the default eventually
(if they don't suck) b) it needs to be obvious to the user how the
"rate" relates to git releases.

This "core.featureAdoptionRate" value seems more like zlib compression
values & unrelated to release numbers. It's also for "performance
features" only but squats a more general name. I suggested
"core.version" & then "core.uiVersion" (in
https://public-inbox.org/git/[email-masked]/).

Regardless of whether we want to pin opt-in early-bird features to
version numbers in some way, which I think is a good idea, but maybe
others disagree. I think if it's "just performance" it's good to put
that in the key name in such a way that we can have "early UI" features,
or other non-UI non-performance.

Thanks for working on this!