but we actually don't care about the extension, whatever comes out of gunzip will actually be just a file, 
and we can't know what type of file yet, without inspecting it first, so I'm using os.path.split to get rid of the extension, and then try again, with magic numbers to see what file this is.

This is needed because people are shipping `blabla.patch.gz`

but yes, I will need to add extra code to check if a certain outputfile is a tar file, and then do a streaming unpack, 
This way we won't need the intermediate file.

So, some changing might happen here (and is probably warranted)

Let's postpone this pull request for a while,