jwm: add desktop file
I have installed alpine 3.9.2 x86_64 standard.
after the install and adding xorg-server setup-xorg-base lxdm jwm
fluxbox xinit and all pertinent packages I still couldn’t start the
window manager.
I noticed that /usr/share/xsessions was missing.
I don’t know if this is a bug or alpine does things differently.
however, after manually creating /usr/share/xsessions/jwm file I can
start jwm normally from lxdm
(from redmine: issue id 10076, created on 2019-03-09)