`ntpath.join()` incorrectly inserts an additional slash when joining an argument onto an incomplete UNC drive with a trailing slash: ```python >>> import ntpath >>> ntpath.join('\\\\server\\share\\foo\\', 'bar') '\\\\server\\share\\foo\\bar' # ok >>> ntpath.join('\\\\server\\share\\', 'foo') '\\\\server\\share\\foo' # ok >>> ntpath.join('\\\\server\\', 'share') '\\\\server\\\\share' # wrong! >>> ntpath.join('\\\\', 'server') '\\\\\\server' # wrong! ``` Before 005e69403d638f9ff8f71e59960c600016e101a4 (3.12), the last test case succeeds because `splitdrive()` doesn't identify `'\\\\'` as a UNC drive. But the third test case is reproducible going back to 3.11 and 3.10. <!-- gh-linked-prs --> ### Linked PRs * gh-103221 <!-- /gh-linked-prs -->