Re: [BuildStream] Proposal: bst artifact subcommand group

[Richard Maw <richard maw codethink co uk>]

On Tue, Jul 24, 2018 at 07:48:33PM +0900, Tristan Van Berkom via Buildstream-list wrote:
> Beyond this:
>
>   o It will be interesting to allow artifact operations to specify
>     elements instead of artifact names, for the cases where you just
>     want to use the artifact who's cache key corresponds to the project
>     state.

This is easy, it's just a matter of loading the element
and asking the cache what ref it would be.

>   o It would also be interesting to move `checkout`, `push` and `pull`
>     commands under the new `artifact` group (deprecating the existing
>     commands).
>
>     This will open up the door to performing checkouts etc at the
>     artifact level instead of only supporting the artifacts who's
>     cache keys correspond to the project state.

This is less easy.

To not duplicate the logic we need to either turn our Artifacts into "Elements",
or re-architect to expose interfaces that operate on Artifacts
and handle Elements by turning them into Artifacts first.

I looked at turning Artifacts into "Elements",
which could be done with custom Project and Loader classes,
but it looks to be more work than I've time for before 1.4.

If `bst checkout` is going to be deprecated in 1.4
you won't be able to use the options for running integration commands
or whether to include dependencies when specifying an element name.

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