After applying the attached patches (based on latest CVS) you should
have a new option available within your version that should also
show up using fgfs --help, the syntax is:
fgfs --min-status={level} --show-aircraft
whereas "level" can be anything between
"alpha","beta","early-production" and "production"
Of course running something like
fgfs --min-status=alpha --show-aircraft
should not return any aircraft right now, as none of the
current aircraft definition files in your base-package is using the
required
<status></status>
tag - but you can easily give it a try by adding something like
<status>alpha</status>
The tag should be placed as a sub-tag within <sim> - so directly behind
the <description> tag would be just fine and straight-forward.