Support multiple version strategies for Librarian::Manifest

[justenwalker]

Summary

As mentioned in PR #150 by @yfeldblum. Lack of Semver 2.0.0 support exposes the need to support multiple version strategies.

This PR attempts to add multi-version support to Manifests (defaulting to GemVersion) and offers SemanticVersion as a built-in strategy that downstream projects can use on by overriding Librarian::Environment

def adapter_manifest_version
  Librarian::ManifestVersion::SemanticVersion
end

Changes

• Add ManifestVersion Module to contain version strategies
• Allow overriding version strategy via Environment#adapter_manifest_version
  • Defaults to GemVersion strategy for backwards compatibility
• Convert Manifest::Version to ManifestVersion::GemVersion strategy
• Add ManifestVersion::SemanticVersion Strategy supporting Semver 2.0.0
  • Relax Semver constraints to support 2-number versions (ie: 1.0)
• Added Specs to test conditions mentioned in semver spec
• Use GemVersion strategy in mock registry

[justenwalker]

any thoughts on this @yfeldblum?

[patcon]

bump?

[justenwalker]

@yfeldblum is there anything you need me to do to make this patch acceptable for merge?

[krobertson]

Bump... would love this functionality as well, since getting bit by using librarian for something that doesn't confirm to ruby's version format.