update Compat for rename of Pkg to OldPkg

[KristofferC]

also temporarily disable the Project file while things are in flux

Somehow I managed to make the #547 branch close itself... -.-.

@StefanKarpinski, @martinholters

[martinholters]

LGTM by itself (shame we have to disable the Project.toml), but do we still plan to add something as Compat.Pkg in the (near) future? That would be Pkg3 on 0.7 and ... Base.Pkg on 0.6?

So the idea would be to use

• Compat.OldPkg if one really needs the old Pkg2 functionality/API, even if that may be of limited value on 0.7
• Compat.Pkg if one needs a way of accessing very basic packaging functionality (add, dir), as is often needed e.g. for CI, compatible with 0.6, 0.7, and onward.

Doesn't sound too bad to me. But I assume the second use to be more common, so maybe we should skip the deprecation?

And of course, if we agree on this as the way forward, README and tests need adjustment.

[KristofferC]

Yes, that makes sense to me. So if this PR is ok for you, I intend to merge JuliaLang/julia#27095 when I fixed CI, then merge this and tag a new Compat, then update the registry and we should be able to release an alpha for 0.7.

[martinholters]

This PR is ok with me, modulo test and README update.

But should we keep Compat.Pkg undeprecated or not? (Yes, suddenly switching Compat.Pkg from Pkg2 to Pkg3 might be breaking. But a deprecation that tells people to use Compat.OldPkg instead of Compat.Pkg when in the majority of cases, they should soon be using Compat.Pkg again soon does not sound too useful.) Or should we make Compat.Pkg be Pkg3 (when available) immediately?

[KristofferC]

But should we keep Compat.Pkg undeprecated or not?

Ok, let's not then. The PR is then as simple as this.

[martinholters]

Sometimes, simple really is best. 😄 And we're surely not doing anything wrong here.

Also, this agrees with what (I perceived) we came to in #547:

• Being able to access Pkg2 on 0.7 will be of little use, probably no need to support that.
• We just let Compat.Pkg become Pkg3 and wait for the complaint to come in.

Bottom line: LGTM. Also, no need to wait for JuliaLang/julia#27095 to merge this, or?

[KristofferC]

No, this should be good to go then. Thanks for your feedback, greatly appreciated!

[martinholters]

We probably should wait a little more to give others a chance to chime in? Having a PR open at least 24 hours if not terribly urgent is a nice rule. OTOH, #547 had been open for a while, so 🤷‍♂️