Add command pack manifest add to add an image to a manifest list

[jjbustamante]

Context

We've been working on the idea to add multi-arch support on CNB. A mentorship project was created on LFX and this feature is part of the efforts to build the Minimal Viable Product (MVP) during the program duration.

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Description

When a manifest list already exists in the docker daemon or in a registry, sometimes the user expects to update it by adding a new image to the manifest list.

Proposed solution

A new feature on Pack can be implemented to help our users. The feature is inspired by the similar functionality in docker or podman

pack manifest add  [OPTIONS] <manifest-list> <manifest> 
  options:
   --all         If the image which should be added to the list or index is itself a list or index, add all of the contents to the local list
   --arch     Set the architecture 
   --os         Set the operating system
   --variant  Set the architecture variant

Describe alternatives you've considered

Additional context

• This feature should be documented somewhere