Re: [PATCH 0/3] revision: refactor ref_excludes to ref_visibility

[Taylor Blau <me@ttaylorr.com>]

On Thu, Jun 22, 2023 at 08:42:24AM -0400, Taylor Blau wrote:
> On Wed, Jun 21, 2023 at 07:35:09PM +0000, John Cai via GitGitGadget wrote:
> > The ref_excludes API is used to tell which refs should be excluded. However,
> > there are times when we would want to add refs to explicitly include as
> > well. 4fe42f326e (pack-refs: teach pack-refs --include option, 2023-05-12)
> > taught pack-refs how to include certain refs, but did it in a more manual
> > way by keeping the ref patterns in a separate string list. Instead, we can
> > easily extend the ref_excludes API to include refs as well, since this use
> > case fits into the API nicely.
>
> After reading this description, I am not sure why you can't "include" a
> reference that would otherwise be excluded by passing the rules:
>
>   - refs/heads/exclude/*
>   - !refs/heads/exclude/but/include/me
>
> (where the '!' prefix in the last rule is what brings back the included
> reference).
>
> But let's read on and see if there is something that I'm missing.

Having read this series in detail, I am puzzled. I don't think that
there is any limitation of the existing reference hiding rules that
wouldn't permit what you're trying to do by adding the list of
references you want to include at the end of the exclude list, so long
as they are each prefixed with the magic "!" sentinel.

I think splitting the list of excluded references into individual
excluded and non-excluded references creates some awkwardness. For one:
excluded references already can cause us to include a reference, so
splitting that behavior across two lists seems difficult to reason
about.

For example, if your excluded list contains:

  - refs/heads/foo
  - refs/heads/bar
  - !refs/heads/foo/baz

and your included lists contains:

  - refs/heads/bar/baz/quux

I am left wondering: why doesn't the rule pertaining to
refs/heads/foo/baz show up in the included list? Likewise, what happens
with refs/heads/bar/baz/quux? It is a child of an excluded rule, so the
question is which list takes priority.

Mostly, I am wondering if I am missing something that would explain why
you couldn't modify the above example's excluded list to contain
something like "!refs/heads/bar/baz/quux", eliminating the need for the
include list entirely.

Thanks,
Taylor