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Issue Description:

This example is adapted from Foundation's test suite (NSURLWithString-parse-absolute-with-relative-029)

func dumpURL(_ url: URL) {
  print("----------------------------------")
  print(url)
  print(url.path)
  print(url.standardized)
  print(url.standardized.path)
}

dumpURL(URL(string: "http://example.com/..///../blow")!)

Outputs the following:

http://example.com/..///../blow
/..///../blow
http://example.com/blow
/blow

This result is incorrect; the standardized path should actually be "//blow".

• The first ".." component is discarded since it is at the start of the path and can't pop anything

• The path then starts with "///..", which is 2 empty components and a ".." component. The ".." pops one of the empties, leaving one remaining empty component

• Finally, the "/blow" component should be added (including its leading slash)

The older RFCs which URL conforms to don't typically specify how ".." components should be resolved in an absolute URL, so it's unclear which behaviour Foundation is attempting to implement, but they do define how those should work when resolving a relative URL:

• RFC-1808, Section 4: Resolving relative URLs

• RFC-2396, Section 5.2: Resolving Relative References to Absolute Form (also has examples in Appendix C)

Additionally, the more recent RFC-3986 does define a more general algorithm:

• RFC-3986, Section 5.2.4: Remove Dot Segments

> The pseudocode also refers to a "remove_dot_segments" routine for
interpreting and removing the special "." and ".." complete path
segments from a referenced path. This is done after the path is
extracted from a reference, whether or not the path was relative, in
order to remove any invalid or extraneous dot-segments prior to
forming the target URI.

Perhaps this is what Foundation is attempting to implement?

All of these references appear to confirm my belief that Foundation is in error, and the correctly-resolved path should be "//blow". Additionally, this is the result returned by the WHATWG URL Standard and modern browsers, including Safari 15 (JSDOM Live URL Viewer)

Additionally, if we add a component, a rather curious thing happens:

dumpURL(URL(string: "http://example.com/..///../blow")!)
dumpURL(URL(string: "http://example.com/../x///../blow")!) // Add a component before triple slashes, now they are not collapsed?!?!?

----------------------------------
http://example.com/..///../blow
/..///../blow
http://example.com/blow
/blow
----------------------------------
http://example.com/../x///../blow
/../x///../blow
http://example.com/x//blow
/x//blow

So if we add a path component before the triple slashes, for some reason they no longer get collapsed. This is just bizarre; I have no idea what's going on here.