Bug report

Bug description:

>>> import posixpath
>>> posixpath.commonpath(["//foo/bar", "//foo/baz"])
'/foo'

Expected: //foo with precisely two leading slashes, see: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13

This can be quite easily solved using posixpath.splitroot, see the PR.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-117201: Handle leading // for posixpath.commonpath #117202
• gh-117201: Handle leading // for posixpath.commonpath #117334