"Sign in using your browser" doesn't work with AppImage

Description

When prompted to sign in to the app, the “Sign in using your browser” option doesn’t work.

Version

GitHub Desktop version: 1.0.11

OS version: Ubuntu 16.04.3

Steps to Reproduce

1. Launch the app for the first time
2. Press buttons until you can choose to sign in in a browser, and do so
3. Go through the OAuth prompts
4. Finish the OAuth prompts, and the redirect to the app doesn’t work – you get prompted (by Chrome) to open xdg-open, but the webpage doesn’t close, and the GitHub app just sits there with the loading spinner until you press Cancel.

Expected behavior: Signing in through a browser should work

Actual behavior: The redirect back to the app doesn’t work

Reproduces how often: Presumably always, at least when using the AppImage

Logs

Can’t find these on Linux, will happily provide if someone tells me where they are

Additional Information

[ascendancyy]

The app protocols need to be added to script/electron-builder-linux.yml. In electron-packager the protocols are only used for mapping to CFBundleURLSchemes. Meanwhile the protocols in the electron-builder config are used to add the MimeType entry to the app’s desktop file.

[theel0ja]

Same issue with .deb version