Calling `setCurrentWorkingDirectory` on `getRealFileSystem` sets the
working directory for the process itself. This is unsafe for clients
such as SourceKit which can process multiple concurrent requests,
and may be used as an in-process library in e.g sourcekit-lsp. Switch
to `createPhysicalFileSystem` instead, where setting the working
directory is done locally on the FileSystem itself.
These tests were relying on specifics of `getUniqueID` that aren't
necessarily true - namely that moving a file from `source` to `dest`
doesn't change the returned ID. They are really just testing
`moveFileIfDifferent`, which doesn't need to make this assumption.
Hamish Knight
Ben Barham
Evan Wilde
practicalswift
Michael Gottesman