VIM and tab to space migration

[Brian Quinlan]

> I use these settings myself, but just now after posting, I realized that
> it is far better to set the preferences on a per-buffer basis, so I
> change my advice to the following:

[snipped]

> And this is *really* all there is to it.

I don't know what this is supposed to do, but it doesn't seem to do what 
I want. Here is the test I performed:

1. create a new file using tab indentation
2. open it in VIM
3. hit the tab key

VIM inserts 4 spaces for the tab so I now have a file containing mixed 
tabs and spaces. Ideally, I would like VIM to be smart enough (like 
every other programmer's editor in the universe) to detect the current 
tab settings in the file and use those.

Cheers,
Brian