Allow `$python_root$` in the `# gazelle:python_visibility` directive

[dougthor42]

🚀 feature request

Relevant Rules

• gazelle

Description

#1784 added the python_visibility directive. #1787 added the python_default_visibility directive, which includes support for injecting the python root via $python_root$ (technically it was #1835 that added the trailing $).

However, python_visibility doesn't support $python_root$, so you end up with cases where sometimes you get to use $python_root$ and other times you have to hard-code it:

# gazelle:python_default_visibility //$python_root$/foo/bar/baz:__subpackages__, //$python_root$/somewhere
# gazelle:python_visibility //src/foo/bar:__pkg__

Describe the solution you'd like

Add support for $python_root$ to gazelle:python_visibility.

Describe alternatives you've considered

N/A

[dougthor42]

/assign @dougthor42