Last modified: 2009-10-28 19:12:59 UTC
Say you have a wiki set called A and a wiki set called B. http://meta.wikimedia.org/wiki/Special:EditWikiSets lists them both and http://meta.wikimedia.org/wiki/Special:EditWikiSets/1 and http://meta.wikimedia.org/wiki/Special:EditWikiSets/2 are places to edit the sets, respectively. However, if I move the set B to the name A, the software would show a success message and http://meta.wikimedia.org/wiki/Special:EditWikiSets will subsequently list only the set B. Set A still exists, though, and can be accessed by directly typing .../1 in the URL field. However, I don't think it's intuitive to be able to move over another set name and shadow it without any warning. So, there should be an error if you try to rename set B to A (since A already exists).
Oh, and another thing. Renaming the second set back to B doesn't automatically make A visible again (it does though after A's been renamed to something else, or likely after any change has been made to it).
Should be fixed in r39741.