Terminal dot segments lose URL path trailing slash and change relative redirects

[Timotty]

Potential issue

httpx.URL drops the trailing slash when the input path ends in /. or /... This changes the request target and where relative redirects resolve, even though RFC 3986 §5.2.4 preserves a trailing / after removing a terminal dot segment.

Minimal reproduction

import httpx

url = httpx.URL("https://example.com/x/y/..")
print(str(url))
print(url.raw_path)
print(url.join("child"))

Actual:

https://example.com/x
b'/x'
https://example.com/child

Expected after normalizing /x/y/.. to /x/:

https://example.com/x/
b'/x/'
https://example.com/x/child

This also reproduces for /x/. and /x/y/.. An in-process MockTransport redirect from /x/y/.. with Location: child requests /x then /child, instead of /x/ then /x/child.

Investigation

httpx/_urlparse.py:447-475, normalize_path(), removes terminal . and .. components without retaining the directory-ending slash. One possible localized fix is to append an empty component when an absolute path ends in /. or /..; regression tests can cover URL construction, .raw_path, .join() and redirects. Is this consistent with HTTPX's intended URL normalization behavior? If maintainers agree, I can submit a focused PR.

Verified against default-branch commit b5addb64f0161ff6bfe94c124ef76f6a1fba5254, HTTPX 0.28.1, Python 3.12.13 on Windows; checked open/closed issues and PRs for terminal dot segments and trailing slashes without finding this case.

AI disclosure: bug discovery assisted by Luna (timotty-responses/luna); reproduction and proposed fix reviewed with OpenCode (GPT-6 Sol). No PR has been published.

[Cha-Imaa]

Normalize first to preserve the trailing slash. Verified with HTTPX 0.28.1

from urllib.parse import urljoin
import httpx

url = httpx.URL(urljoin("https://example.com/", "/x/y/.."))
print(url.join("child"))

https://example.com/x/child