Be more git compliant when resolving references

It looks like LibGit2Sharp is not that git.git compliant when it comes to weirdly named references. Let's fix this!

Given a repo with a tag refs/tags/refs/tags/v1.0

• TagCollection["v1.0"] shouldn't resolve anything
• TagCollection["refs/tags/v1.0"] should correctly resolve it
• TagCollection["refs/tags/refs/tags/v1.0"] should correctly resolve it

Given a repo with two tags refs/tags/refs/tags/v1.0 and refs/tags/v1.0

• TagCollection["v1.0"] should resolve refs/tags/v1.0
• TagCollection["refs/tags/v1.0"] should resolve refs/tags/v1.0
• TagCollection["refs/tags/refs/tags/v1.0"] should resolve refs/tags/refs/tags/v1.0

It would make sense to make BranchCollection consistent with this behavior as well.

Given a repo with a tag refs/tags/v1.0 and a branch refs/heads/v1.0

• TagCollection["v1.0"] should resolve refs/tags/v1.0
• BranchCollection["v1.0"] should resolve refs/heads/v1.0

TagCollection と BranchCollection の検索エントリポイントから開始し、参照名がどのように解決されるかを追跡してください。記載されているリポジトリを再現し、タグとブランチの検索が各ケースで指定された参照を正確に返すことを検証してください。