The central enemy of reliability is complexity.
― Geer et al., 2003
Pretty smooth sailing so far. However, there was one minor glitch and it wasn’t immediately obvious to me, how to fix it:
I could not set the Developer Edition installation as my default browser in Gnome (with Gnome Shell on Fedora 22). I did a manual installation of the Firefox Developer Edition and could run and use it. But as Gnome wasn’t aware of it, I could not select it in the Gnome “Default Applications” settings, neither did it work from within the Firefox settings.
Here is how I solved it with two steps:
1. Create a .desktop file (e.g. “firefox_dev.desktop”) for the Developer Edition installation in ~/.local/share/applications
[Desktop Entry] Encoding=UTF-8 Version=1.0 Type=Application NoDisplay=false Exec=/opt/firefox_dev/firefox %u Name=Firefox Developer Edition Terminal=false Icon=/opt/firefox_dev/browser/icons/mozicon128.png Categories=Application;Network;X-Developer; Comment=Custom definition for Firefox Developer Edition
You may need to adjust the paths to reflect your installation path.
2. Set a MIME-type rule for this .desktop file
gvfs-mime --set x-scheme-handler/http firefox_dev.desktop
Be aware, that the .desktop file is referred to without any paths. Use the plain file name, otherwise you end up getting an error message.
After doing that you should have the Firefox Developer Edition set as your default browser, it should show up in the settings “Default Applications” and you should get a nice icon in the activities search for it.