Only very rarely used. Easily migrated in favour of:
##### Detect main page
Instead of using wgMainPageTitle to compare with wgTitle or wgPagename, use `wgIsMainPage` instead.
##### Linking to the main page
For creating an anchor link that will end up on the main page, use `wgScript`, or `title=`. It will always resolve to the main page by default.
##### Getting the main page configuration value
When the configuration value from the current site is really needed. It can be retrieved in one of two ways:
* For gadgets, use the Siteinfo API.
* For extensions, use `Title::newMainPage()` and bundle its return value with the module that needs it.
Originally added in 2009 with cf75bdf4ba ([r54384](https://www.mediawiki.org/wiki/Special:Code/MediaWiki/r54384)) and moved to the startup module in 2010 with a99f9ec28b9aa9d ([r72772](https://www.mediawiki.org/wiki/Special:Code/MediaWiki/r72772)).