Regex changes from [52376] are reverted to restore the original regex patterns. Why? [52376] used an include characters pattern, which was too limiting. It did not account for localized characters, such as `é`, or other valid directory name characters.
The original theme directory regex pattern, i.e. `[^.\/]+(?:\/[^.\/]+)?` excluded the period `.` character. Removing the `.` character resolves the reported issue by allowing matching for `themes/theme-dirname-1.0/` or `themes/<subdirname>/theme-dirname-1.0/`.
As the pattern used an exclude approach, all characters are valid for matching except for `/`. However, not all characters are cross-platform valid for directory names. For example, the characters `/:<>*?"|` are not valid on Windows OS. The pattern now excludes those characters.
The theme's directory (or subdirectory) name pattern matching is now used in `WP_REST_Global_Styles_Controller`, `WP_REST_Templates_Controller`, and `WP_REST_Themes_Controller`.
Follow-up to [51003], [52051], [52275], [52376].
Props costdev, hellofromTonya, spacedmonkey, TimothyBlynJacobs, bijayyadav, kafleg.
Fixes#54596.
Built from https://develop.svn.wordpress.org/trunk@52399
git-svn-id: http://core.svn.wordpress.org/trunk@51991 1a063a9b-81f0-0310-95a4-ce76da25c4cd
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