config: add a ProgramData level - #3475

I have good news for you. It turns out that %PROGRAMDATA% is a magical wasteland of terrible. It's not actually world-writable, as was claimed in the first PR, which makes a lot of sense. Instead, there's some magical redirection that goes on if you don't have permission to write to it, where your file(s) are magically shunted off to a place like %LOCALAPPDATA%\VirtualStore\ProgramData\....

I don't know what subsequent reads of %PROGRAMDATA%\... paths do - maybe they look in your per-user %PROGRAMDATA% first ...?

This is really abysmal and I'm sorry that this crime scene has some of my fingerprints on it.

On my dev box I have C:\ProgramData\Git\config which I can see with explorer, and before adding me as having full control over the file, git_filebuf would fail to rename the lockfile to the final location with a permission error, so I don't know if G4W does something special or what, but it does seem to exist as a regular file (at least it behaves like it). The changes made by the test do persist as well (I can open it with notepad and see the new variable).

I'm not sure if that means anything, but it looks like the test will have to make sure to create the directory (I was hoping whatever git installation it has would work the same way as on my box, which evidently it does not).