* Added line in `UndoLastCommitAction` to get the previous commit msg and store in `IStorageService`.
* Added `UpdateCommitInputPrevCommitMsg` that checks for that key in storage, and use it then remove it if it exists.
  * This does not suffer from the previous bug that blanked out the commit msg if you unstage a file.
  * Added a clause if the undo last commit fails to remove the key from storage. This way, it doesn't stay in there and get used later (I was scratching my head when it showed up later).