Define "strip the fragment directive" generically, without the extra Document steps

[tabatkins]

I'm defining how fragment-only CSS urls (like url(#foo)) work, and need to get the fragment so I can search for a matching ID in the tree. If the url is #foo:~:text=foo, presumably I want to strip the directive and just search for "foo" as the ID, but the spec doesn't currently define a generic algorithm allowing me to do this; it bundles this behavior into also updating some Document state.

Could I get that algo abstracted out, so it takes a raw fragment string and returns a pair of (fragment, directive) strings?

[bokand]

Yeah, that makes sense. I'm going to be upstreaming the spec as part of #195 so I'll make sure I do that as part of that work. I'm hoping to work on that this month.