[MWRAPPER-86] Trim repourl and other checks; tests

[bmarwell]

• first commit tries to fixes the problem, except I actually used - 2 instead of - 1
• Refactored the methods a bit to make them easier to test
• Added a few tests for the most common cases
• Opened a field and method for testing to protected
• Don't use too short repo URLs where not even the protocol could fit.

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