The concept of this seems pretty good! If I understand it correctly this is not for creating transport packages for me to redistribute (that would be something like My Component) but instead this pulls the latest code from Github and installs it into MODX?
I've installed this and watched the tutorial YouTube videos and read the wiki.
I seem to be getting stuck with the paths, I've setup a /packages/ folder on my website root (not the same as the /core/packages/ folder), and set the system setting gitpackagemanagement.packages_base_url to /packages/ (with the forward slash at both ends) and the gitpackagemanagement.packages_di setting to just packages (without any forward slashes).
In your tutorial you recommend using UrlShortener because it has a ready-made config file, so I've clicked the Download ZIP link here and uploaded it to the /packages/ folder into its own /UrlShortener/
https://github.com/TheBoxer/UrlShortener
Then, when I run the Git Package Manager CMP and add a new package, using just UrlShortener as the folder name.
I then see an error which says "This package folder does not contain config file." Although there's a config file here /packages/UrlShortener/_build/config.json