`/a/**` is understood by `Path.full_match` as `/a` followed by multiple segments, at least one

Bug report

Bug description:

/a/** is understood by Path.full_match as "/a followed by multiple segments, at least one", instead of "/a followed by multiple segments, including zero".

From https://docs.python.org/3/library/pathlib.html#pathlib-pattern-language

** (entire segment)
Matches any number of file or directory segments, including zero.

# one segment per **
Path('/a/b').full_match('/a/**') # True
# zero segments per **
Path('/a').full_match('/a/**') # False - expected True
# interestingly
Path('/').full_match('/**') # True

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-151479

从 pathlib Path.full_match 入口开始，将其行为与针对 ** 所记录的模式语言进行比较。重现 /a/** 和 /** 示例，然后添加回归覆盖，表明 ** 匹配零个段；链接的 PR gh-151479 表明相关工作已经在进行中。