correction to renameCollectionSameDB action type

[bgrabar]

Ready for merge. Corrections to the definition of the renameCollectionSameDB action. Reviewed & approved by Andreas.

[tychoish]

You made this change once, which was merged as f3be46d. Kay and I spent a while with the source code, and made a few very minor changes, committed as bf2bccc, which conveys the same point and introduces a little redundancy, but I think is cognitively less difficult to untangle (because it's a bit logically redundant,)

Are there active objections to the current wording? If there aren't I'd like to keep the text as it is.

https://github.com/mongodb/mongo/blob/master/src/mongo/db/commands/rename_collection_common.cpp

[bgrabar]

There's a couple of important changes according to Andreas:

1. The requirement that the user either have "find" on the source or not have "find" on the destination always applies, whether or not the collection already exists.
2. The dropCollection action is required on the destination collection, not the source.

[tychoish]

merged!