WIP: cli safe push (browse instead of force)

[drernie]

Description

TODO

• [ ] Unit tests
• [ ] Automated tests (e.g. Preflight)
• [ ] Confirm that this change meets security best practices and does not violate the security model
• [ ] Documentation
  • [ ] Python: Run build.py for new docstrings
  • [ ] Markdown somewhere in docs/**/*.md that explains the feature to end users (said .md files should be linked from SUMMARY.md so they appear on https://docs.quiltdata.com)
  • [ ] Markdown docs for developers
• [ ] Changelog entry (skip if change is not significant to end users, e.g. docs only)