A mistyped or unsupported flag (e.g. --automation-write-roots) used to be
dropped silently, so the app started unconfined. It now exits 2 with
'unknown option', like a bad automation root. A bare -- ends the options.
Adds a desktop control-channel test that file.save / file.saveAs outside the
write root are refused and create nothing, while saves inside succeed, and
documents that the root flags arrived in 0.7.0 (0.6.0 ignores them).
skylar taylor-barrick
4b7e0afd19