Add non-mocked test for symlink

[coyotte508]

Alternative to #1307

Fix #1306

I was just too confused by the src/dst params, nodej's official docs could be clearer too.

Now the params are explictly named and there is a real test to check the filesystem contents.

By the way, it's a copy operation not a rename (because it was already the case, the new_blob param was never passed)

Also took the opportunty to use relative symlinks cc @Wauplin for better windows support

cc @jeffmaury @axel7083

[jeffmaury]

I just a little bit concerned because the new tests don't pass on Windows which is why createSymlink has been created and as I'm on Windows it will make my life harder to check I'm not introducing regression

[coyotte508]

I just a little bit concerned because the new tests don't pass on Windows which is why createSymlink has been created and as I'm on Windows it will make my life harder to check I'm not introducing regression

Ok, I added a mocked test on linux, where I just fail the symlink function to behave like it does on windows.

And in the other tests, instead of expect(stats.isSymbolicLink()).toBe(true);, I added expect(stats.isSymbolicLink()).toBe(process.platform !== "win32");

Hopefully the tests will now work for you on windows with those changes (and linux at the same time)

[jeffmaury]

LGTM. But there are changes in XetBlob that seem unrelated

[jeffmaury]

Not sure to get why we are changing the flag here

[coyotte508]

It's to reset the function once it's called. (so it doesn't impact other tests)

Could be done more elegantly