Re: command-line tweaking of "Open With..." settings?

An off-list responder pointed me to

  http://doc.trolltech.com/qq/qq12-mac-events.html

which seems to be saying that I should edit my App's Info.plist file
to change the following lines:

                        <key>CFBundleTypeExtensions</key>
                        <array>
                                <string>*</string>
                        </array>

to

                        <key>CFBundleTypeExtensions</key>
                        <array>
                                <string>xyz</string>
                        </array>
                        <key>LSIsAppleDefaultForType</key>
                        <true/>

If I do this, then Drag-copy the App to the Applications folder, the
magic takes effect.  I'd rather keep the App where it is, however.
Is there an easy way to tell OSX to pay attention to the Info.plist?

-r
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