Add warning message when .git directory is not selected #46
Description
Steps to reproduce:
1: When selecting a directory, select the repo folder itself and not the (hidden) .git folder within.
2: This leads to a seemingly "endless" loop where 'Loading ..' never ends.
Motivation:
As a new user of the app, I was skimming the documentation and didn't read the fine print about selecting the .git folder inside the repository. (I do think the documentation is good and well written; I just happened to miss it).
If you can realistically only select the .git folder (or subfolders), then some notification/warning would make you understand why the repo is not being loaded properly when selecting the wrong folder.