[[!template  id=gitbranch branch=chrismgray/exclusive-hooks author="[[chrismgray]]"]]

Sometimes plugins register a function with `hook`, but they only want
the function called with the content that they know how to deal with.
Normally, this means that they call `pagetype` first thing in the
function, determine if they know how to deal with the content, and
only do anything if they do.  

This is a bit wasteful in itself, but for external plugins, it's
really bad.  For functions like `scan` and `linkify`, where the entire
page is sent back and forth over `stdout` and `stdin`, it really slows
things down.  

Thus, I propose that there be a new optional parameter to `hook` that
tells it that the function should only be called for files whose type
is the same as the id of the plugin calling `hook`.  I have called
this parameter `exclusive` in my branch, but this might not be the
best name.

[[!tag patch]]

> It's an interesting idea, but it might be more useful if it was more generalized, say, by making it a filter, where the parameter is a regexp.
> 
> --[[KathrynAndersen]]

>> Would it make more sense as a pagespec?  That might be a bit more hard to implement, but would certainly fix the naming issue.
>>
>> --[[chrismgray]]

>>> Considering where it would be called, a pagespec might be overkill. --[[KathrynAndersen]]