Description

This PR updates the Client interface to allow push operations to:

• Prepare a "staging area" for the full SBOM external reference graph
• Recursively add all externally referenced SBOMs to this staging area
• Do a single push operation containing all staged SBOMs

It also updates the existing Git push operation to use this pattern.

Depends on #153 being merged first (comparison of changes)

Fixes #154

Type of change

• Refactor/enhancement

How Has This Been Tested?

• Stand up temporary Git server for testing push, pull, and clone

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings