In do_git_gui the path of the git executable has to be put into a
list, otherwise calling it will fail when when spaces are present
in its path.
Reported-by: NHeiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: NJens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>