Epic: How does a repo/index show packages?

[msarahan]

This is a epic. Please update the issue or post links in comments to PRs or repos that implement designs for these questions.

Assuming that we have two or more variants of a package, with filenames that are somehow non-overlapping, how should package repositories/indexes show these files?

• Are filenames meaningful enough to be used directly?
• Can filenames be selected by variant? In other words, can the variant be used in a way related to platform tags? Note: it has already been established that using variants in platform tags scales poorly and is not an option.
• Does the repository need to host some file or aggregate of file info indicating which variants are available?
• Does the repository indicate priority among variants?
• Does the repository indicate which metadata providers are necessary in order to choose between the available variants?