Fix double paths in extended source descriptions.

Cherry-pick of 4a2f62a47a71615393c2e963799e2b7184542c7f.
Be a bit more strict in working directory detection in souce_descriptions.
Missed .simplecov in Unparser renaming.
Merge branch 'master' into absolute-paths

Conflicts:
	lib/fig/not_yet_parsed_package.rb
Missed invocation of renamed method in repository.rb.