[vbox-dev] Setting IMachine::snapshotFolder to "." no longer works in VBox 4

[Benjamin Gilbert]

Hello,

In VBox 3.2 and earlier, IMachine::snapshotFolder could be set to "." to 
store snapshots directly in the machine folder.  If this is done under 
current VBox, the Machine tag in the machine XML is written out without 
any snapshotFolder attribute, causing the snapshotFolder to revert to 
the default ("Snapshots") the next time the machine is loaded.

The cause appears to be the fact that the SnapshotFolder COMSETTER now 
uses copyPathRelativeToMachine() to calculate the relative path to be 
stored in the MachineUserData from the absolute path to the snapshot 
folder.  If the path passed to copyPathRelativeToMachine() is equal to 
the machine folder, copyPathRelativeToMachine() incorrectly returns a 
zero-length string rather than ".".  This causes the settings writer not 
to write the attribute.

--Benjamin Gilbert