Aggregate publish buildpack command

[jromero]

Description

As a buildpack user, I'd like to run a single command instead of two to package and push a buildpack to a registry.

Today, I must run both commands:

pack package-buildpack <image-name(out)> -c <config(in)>
pack register-buildpack <image-name(in)>

Proposed solution

The proposed solution as discussed as part of RFC #44:

# package + register
pack publish-buildpack <image-name> [-r <registry-name>] -c <config(in)>

Describe alternatives you've considered

As an alternative a single flag can be added to package-buildpack that does the registration.

pack package-buildpack <image-name(out)> <config(in)> --register <registry-name>

Additional context

• This feature should be documented somewhere

[dfreilich]

Hmm. With the number of commands we have for buildpacks, I would find register vs publish to be confusing, almost perhaps aliases of each other. I'd probably rather adding it as a flag to package-buildpack, similar to our --publish flag for build