xdg-open should allow user to force "desktop environment" detection

[John Carlyle-Clarke]

Binary package hint: xdg-utils

The xdg-open code attempts to detect a desktop environment (GNOME, KDE, XFCE4, other) and choose a way of opening files accordingly.

Users of Fluxbox, Openbox and other WM's may have gnome-open or the corresponding KDE or XFCE components installed and may wish xdg-open to use them.

detectDE() could have code added to check for a variable - say XDG_OPEN_FORCE_DE - and use that value (kde, gnome, xfce, generic) instead of attemtpting a detection if it is present.

[Nicholas Guriev (mymedia)]

Such a variable to simulate any DE has been already invented. It is named XDG_CURRENT_DESKTOP. To get a glimpse how to use it, see test cases. xdg-utils first try to use DE specific tools and, in case of error, fallback to internal implementations for generic mode.

https://git.launchpad.net/ubuntu/+source/xdg-utils/tree/autotests/test-lib.sh?id=9df7480816442225cc59373d62a475247318b0d8#n55