Convert Category to Tag when Cat. already exists as tag results in warning of duplicate entry

[foolswisdom]

Convert Category to Tag when Cat. already exists as tag results in warning of duplicate entry

ENV: WP trunk r5976 (2.3beta1+)

Repro:

1. Create a post with category and tag of 'same'
   
2. Convert 'same' category to tag

RESULTS

Converting category #4...

WordPress database error: [Duplicate entry '4-post_tag' for key 2]
UPDATE wp_term_taxonomy SET taxonomy = 'post_tag' WHERE term_id = '4' AND taxonomy = 'category'
Converted successfully.

[ryan]

(In [5980]) Don't convert category to tag if tag of the same name already exists. fixes #4864

[foolswisdom]

(In [6080]) If a category is already a tag, don't put it in the list of categories to convert. fixes #4955