Any way to not load it on every request?
Maybe use require_once() on both main file and class file (in SyntaxHighlight_GeSHi::initialise())?
require_once() is used instead of require() on r52550.
Better, but the original issues is still valid. Is there any hooks that it would only be checked when viewing Special:Version?
Check for file existence, open the file and read through until 'GESHI_VERSION' occurs and read the value on the value of GESHI_VERSION. After this, close the file.
Is that read the file stright through is faster than load the required file using require()?
No it would not be faster. Nikerabbit: no, there is no hook. I would suggest just not implementing the feature.
Seems the hook listed in Manual:Hooks/SpecialVersionExtensionTypes can be used to get the version information when Special:Version is loaded.
Redone in r52642.
Revert this, it is slow.
Reverted on r52555.