Help specs migrate to new terms for a concept.

[jyasskin]

For example, whatwg/html#1357 renamed "allowed to show a popup" to "triggered by user activation". It left the old id in place so that links from built specs would keep working, but <a>allowed to show a popup</a> now causes a

LINK ERROR: No 'dfn' refs found for 'allowed to show a popup'.

when rebuilding the spec without any indication of what new term to use. It'd be nice if there were a breadcrumb @domenic could have left to map the old ID to the new one. For example,

<dfn data-export
     id="triggered-by-user-activation"
     data-deprecated-lt="allowed to show a popup">triggered by user activation</dfn>

[tabatkins]

That's what lt is for normally. <dfn lt="triggered by user activation | allowed to show a popup">triggered by user activation</dfn> works just fine.

(I'm also building a spider as my Rust learning project that will track autolink usage across specs so you'll have a better idea of what you're breaking if you change terms.)

[tabatkins]

Oh but wait, I see the deal, you still want specs to migrate to the new term, not just silently link to the new one with the old text. Okay. This sounds like it should be part of my "support obsoleting terms" project.