Redirect Name Requests Correctly with Default Permalinks

[filosofo]

Suppose a post has the slug

an-exciting-post-title

but someone requests

/?name=an-exciting-post

Then redirect_guess_404_permalink() correctly guesses the permalink for that post, but the incorrect, partial name argument is retained:

/?p=123&name=an-exciting-post

and so the posts query fails.

Instead, when redirect_guess_404_permalink() returns a permalink that doesn't have a name argument, the old, incorrect name argument should be removed from the final redirect URL.

Note that in this patch I am using the fix appearing in the patch on #15774, because this patch uses some of the work done there. Applying this patch will also fix #15774.

[markjaquith]

(In [17031]) Strip partial name= parameters when doing canonical redirection on them with default permalinks. props filosofo. fixes #15775