Re: [Libguestfs] [PATCH] v2v: -o null: Force output format to be raw sparse.

When converting and throwing away the output (-o null), the input format should not really matter. However it does currently matter for a couple of reasons: (1) If the input is not raw or qcow2, then you'll get the error below because virt-v2v wants to write the same output format as input format but only allows raw or qcow2 as output formats: virt-v2v: error: output format should be 'raw' or 'qcow2'. (2) If you use -o null -oa preallocated then a non-sparse temporary disk is created before being deleted, but that just wastes disk space for no reason. Therefore this change (i) prevents '-o null -oa preallocated' from being specified on the command line, (ii) prevents '-o null -of <anything>', (iii) forces the output (temporary file) to be raw sparse. ---