Reference Link Aliasing or Nesting

[Crissov]

It has been suggested before to turn incomplete Link Reference Definitions into something more useful:

Turning empty link definitions into anchors

Currently CommonMark doesn’t allow reference link definitions without a target: [foo]: [foo] In this respect it is in line with most implementations, though a few treat this as a link with an empty URL. This seems a waste of good syntx. What if an empty reference definition were given a special meaning as an anchor, as illustrated by the following (which would have been really handy in writing the spec document): [link text]: The link text cannot contain links, though it may contain image…

I was wondering whether it would make sense to allow multiple labels for a single link destination (and title), i.e. introduce aliases, e.g. to explicitly and implicitly link to the most recent version of a specification.

[cm]: 
[cm29]: https://spec.commonmark.org/0.29/
[cm28]: https://spec.commonmark.org/0.28/

or allow reference links within reference link definitions (risking infinite loops):

[cm]: [cm29]
[cm28]: https://spec.commonmark.org/0.28/
[cm29]: https://spec.commonmark.org/0.29/

The latter would be useful in case the title (or another, extended attribute) should differ, but the URL should stay the same:

[foo]: foo.pdf
[bar]: [foo] "see bar section in particular"
[baz]: [foo] "see baz section in particular"

With URL Templates (RFC 6570) built-in, this would become really powerful:

[foo]: foo.pdf{#label} "see {label} section in particular"
[bar]: [foo] 
[baz]: [foo]

Basic example

Reference link aliases
======================

* [foo][]
* [bar][]
* [baz][]
* [quz][]
* [dlr][]

______

[foo]:

[bar]: http://example.org

[foo]:
[baz]: http://example.com

[foo]:[quz]: http://example.edu

[foo]: [dlr]: http://example.mil

[foo]
[sit]: http://example.net

[foo][amt]: http://example.arpa

Dingus
Babelmark3