Support `package` for cfn-cli

[wbingli]

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For a resource development CI/CD pipeline, customer need to make a RPDK package only during build time.

Currently cf-cli submit --dry-run will generate a package without submit. But it would be great to have package or build command to do only build and package to generate artifact.

[tobywf]

we have to be mindful of not inserting ourselves into native build processes too much, to preserve the developer experience, so i'm not sure "build" make sense, especially outside a Java perspective. but i look forward to seeing a PR that implements package with the existing submit/dry-run code, as long as the changes are small, and the workflow does not become confusing (e.g. questions like do I have to run "package" before "submit"?)

[wbingli]

Agree on the comment on build command as we don't want to stick with one build tool. Let's do package only now.

[johnttompkins]

what's the difference between a package command and submit --dryrun?

[wbingli]

No functional difference. A better name.

[richardhboyd]

submit —dry-run implies that it will also validate if I have the appropriate permissions to execute the submission. I believe package more accurately reflects what the cfn CLI is actually doing.

[benbridts]

This is very similar to https://github.com/aws-cloudformation/cloudformation-cli/issues/368

[richardhboyd]

I think the difference between the two is the name of the command. cfn submit --dry-run makes a user think it will validate that a bucket exists with the right permissions and the current user has sufficient privileges to perform a submit. package is an entirely local operation that should be able to execute even without IAM credentials.