Explain check for ../wp-settings.php when getting ../wp-config.php

[mattheweppelsheimer]

In wp-load.php, when searching for wp-config.php in the parent directory, we abort if wp-settings.php is also in the parent directory. The reason isn't super clear.

[mattheweppelsheimer]

explain check for wp-settings.php in parent before loading wp-config.php in parent

[mattheweppelsheimer]

Patch adds the following docs to explain:

/*
 * Only get wp-config.php from the parent directory
 * if wp-settings.php is not also in the parent directory, to
 * avoid cases where the current directory is a nested
 * installation, e.g. / is WordPressA and /blog/ is WordPressB.
 */

[mattheweppelsheimer]

And thank you @dd32 for clarifying the reason for me.

[DrewAPicture]

In 31463:

Add inline documentation to clarify the reasoning behind the various conditions that control how WP is loaded.

Props mattheweppelsheimer for the initial patch.
Fixes #30935.