Duplicate `/sites/{blog_id}` path in upload directory still persists

[christianwach]

I have a multi-network which I converted from a legacy ms_files_rewriting structure to a default wp-content/uploads/sites/{blog_id} structure. I've been using a fork of this plugin that fixed the path duplication issue a while back.

For the first time in a while, I needed to create a new network, so decided to upgrade to version 3.0.0 of this plugin to see if this PR had indeed fixed the /sites/{blog_id}/sites/{blog_id} issue - but it doesn't seem to have done so - that was indeed how the new network was set up.

In fact the only solution that I can find (at least for compatibility with a default post WordPress 3.5 system) is to set upload_path and upload_url_path to an empty string. WordPress seems to handle the subdirectories just fine as long as upload_path is empty.

I don't really have solutions for the variants that must be out there now, i.e. networks with ms_files_rewriting, networks with UPLOAD defined, as well as networks with /sites/{blog_id}/sites/{blog_id} - but to implement /sites/{blog_id}, empty upload_path and upload_url_path options seem to be the way to go.

[christianwach]

FWIW, filters for upload_path and upload_url_path before this line could be useful additions so that there's some external control over these options during the add_network process. Or perhaps adding $new_blog_id to the 'add_network' filter might work?

[christianwach]

For anyone in my situation who wants to keep uploads paths to just /sites/{blog_id}, this MU-Plugin prevents upload_path and upload_url_path from being set to anything but empty and fixes the duplicate path issue.