How does a merge take place in Area 51?

Question

I have seen many suggestions to merge proposals. How is this done?

I get the impression that, even on very popular merge proposals, everyone's waiting for "the powers that be" to do a merge. Do the powers that be do this, somehow, or are we waiting in vain? If there are multiple proposals I think should be merged, is the proper solution to open a new proposal that encompasses them all?

Let me offer a few examples, as the answer may vary depending on the state of the proposals/sites in question. What is the proper method to merge proposals in each of the following scenarios? And assume for the sake of argument that the topic matters are not duplicates (if they were, one would be closed simply as a duplicate), but are closely enough related that a merge request would actually get some traction.

1. Two (or more) sites in 'Definition' stage.
2. Two (or more) sites in 'Commitment' stage.
3. One site in 'Definition', one in 'Commitment'.
4. One site in 'Definition', one live (either in beta, or permanent).
5. One site in 'Commitment', one live.

Answer 1

See the definitive answer from Robert Cartaino♦, the Director of Community Development for the Stack Exchange Network.

My previous answer:

This has been asked on meta.SO a couple of times. I think the answer is in there somewhere:

• this one in particular: https://meta.stackoverflow.com/a/78030/164022
• see also: https://meta.stackoverflow.com/q/58475/164022
• and: https://meta.stackoverflow.com/q/54697/164022
• and: https://meta.stackoverflow.com/q/84406/164022

It looks like tagging a discussion here on discuss.area51 with the change-request tag is part of the trigger to start a manual process of merging.

I see there's a merge-request tag too, just to confuse things. Probably best to use that one. (I'm guessing using both would be overkill)