I've made the following changes, which can be tested on commons.prototype.wikimedia.org

1. Refactored UploadStash to use the database for metadata storage. This enables simultaneous multiple-file upload (not multi-file selection, yet).

2. Added support for TitleBlacklist in the UI (via the new TitleBlacklist API). Currently the blacklist is the file I use for API unit tests, which looks like so:

.*[Ff]ail.* .*[Nn]yancat.* <errmsg=blacklisted-nyancat>

So, it will only fail on titles that contain "fail" or "nyancat". It should be straightforward to use a wiki page instead, if anyone feels the need to test things that file doesn't include. I don't actually have permission to create the "MediaWiki:Blacklisted-nyancat" page, so if someone wants to test custom errors, it'd make sense to make that (for a couple languages... for /fr, I recommend the text "C'est l'erreur Chat Nyan.") They should work fine, though, since that's all existing code in TitleBlacklist.

The user sees the custom error when s/he clicks the "More Info" link. That message is often very long and informative, and wouldn't fit on the page inline.

3. There is a blacklist error reporting page, at http://commons.prototype.wikimedia.org/wiki/UploadWizard_blacklist_issues When a title is blacklisted, the user has the option of commenting on that entry with the "Send Feedback" link. The location of this page is configurable in LocalSettings.php.

I think that's it. We're looking at deploying the first change on Wednesday, and the others next week (barring serious issues).

-Ian