cli: Workaround UNC path fs::canonicalize return

[alexheretic]

• Reported in windows rls stderr: thread 'main' has overflowed its stack #838, also related: std::fs::canonicalize returns UNC paths on Windows, and a lot of software doesn't support UNC paths rust#42869
• Update rustfmt -> 3d85084a

[Xanewok]

@alexheretic I know this is a workaround, but do you think it might be a good idea to include a Windows-only test?

[alexheretic]

I thought about that, but "\\?\" UNC just won't work wherever it's from so the windows check seemed redundant extra code. Can't see it coming from any other platform though, I think linking to the issue should allow removal if this ever gets solved in canonicalize

[Xanewok]

I meant a Windows-only unit/regression test for the url func, so we'll know if/when that fails, but I'm not sure if it's even possible to create a reliable test for this use case in the AppVeyor CI 🙁

The comment alone is enough, just wanted to ask if it's a good idea to include such a test in the first place.

[alexheretic]

Ah yes, a unit test could work. A better test is harder as the source of the path is std::env::current_dir().

The unit test would pretty much just check that it works though, so maybe not a huge value.

[alexheretic]

I've added one now, left it running on all platforms as then all devs will keep it compiling (and it's a fast test).

[Xanewok]

Sorry for the delay and thanks for adding the test!