Save Main site id as a network option

[spacedmonkey]

In #29684 the idea of saving the main site id as a network option was floated. It has a number of briefs, including.

• Ability to change main site id
• Easy to find main site id using database query
• Result is cached and never needs to be looked up.

[johnjamesjacoby]

When will the domain and path of the main site ID not match what’s in wp_blogs?

Doesn’t it put the cart before the horse to store this site ID in network meta, because wp_blogs needs to get queried to know which site and network to load anyways, and the network knows what it’s main site is?

[jeremyfelt]

Sorry to cut this off, and thanks for being proactive @spacedmonkey, but I think this ticket can be considered a duplicate of #29684, where the conversation about how best to determine the network's main site ID has been happening. That needs to be resolved before a ticket like this can be effective. And, if we do end up storing it as a network option, then the patch on #29684 should cover that initial storage as well.

@johnjamesjacoby There's a bit of back and forth around this on #29684. Can you chime in there?