Las week I translated the Flatpak documentation to Spanish. Is already available here http://flatpak.readthedocs.io/es/latest/ .
I hope it could serve to promote the adoption of Flatpak. If you are following the translated tutorial to pack your app, I would like to receive your feedback.
It also served me to refresh the details.
After packaging GeoGebra I came aware how the fetch of
works. This option is usually used to refer external data that won't
be bundled with the package, either for licensing or other reasons (in
the case of GeoGebra the license doesn't allow it). I found odd that
the same extra-data had to be downloaded again each time I ran my
tests even if using a local repository.
So I suggested on IRC a caching directory in user space for extra-data. Looking at the flatpak sources I found a TODO line about storing partial data and resumable downloads. This enhacement is along the lines of what I wanted. So I proposed the caching directory as a first step for this https://github.com/flatpak/flatpak/pull/873 .