Hi Colomban,
RE your discussion on IRC about $subject
To save you searching, some info about g_spawn not working (right) on windows, and that it won't be fixed:
http://article.gmane.org/gmane.editors.geany.devel/583
and it appears that it was always recognised that splitting on space wasn't an elegant way of generating argv for windows, and the problems that causes for filenames containing spaces, but nobody has been concerned enough to fix it :) see:
http://lists.uvena.de/geany/2007-November/002082.html
There is no discussion on why windows commands were used in the first place, but given the first reference above I guess it might still not be possible to avoid it.
Cheers Lex