[vbox-dev] Preparations for vbox-unattended; Allowing "unknown" Guest OS types

[Alexey Eromenko]

Vbox-unattended may create lots and lots of os-types in the future.
Like hundreds.

But this problem exists in Oracle VirtualBox also, when tryiong to
degrade to older version.
Today, older VirtualBox cannot open VMs, that were created with a new OS type.

For example if I have created a Windows 10 VM (with v5.0), then
degraded VirtualBox, and try to start it with older VBox 4.3.20, it
will show me "VM inaccessible" and "OStype error" and I won't be able
to start such VM.

One possible solution, is just always accepting "Unknown OS" type, if
future OS type os not in list.

In file "VirtualBoxImpl.cpp", VirtualBox::getGuestOSType()

I just changed
"    return (aType) ? S_OK :
        setError(E_INVALIDARG,
                 tr("'%s' is not a valid Guest OS type"),
                 aId.c_str());"
to

"return S_OK;"

And it works for me.
I'm not yet sure if there are any bad consequences from it.
I think getting "VM inaccessible" error just because you have degraded
to an older version of VirtualBox is wrong.
-- 
-Alexey Eromenko "Technologov"