Sanitize the ends of folder source paths (#1341)

* Sanitize the ends of folder source paths

Setting the source: `/foo/bar` is _sometimes_ different from `/foo/bar/` even if `bar` is a folder in both cases. The result of this is that we often run into a race condition where we have two objects with the same hash but different properties. This fixes #1339 and #1131.

* Update CHANGELOG.md

* Update TargetSource.swift

* Update TargetSource.swift

* Update TargetSource.swift