releases: Expand rel-latest macro

[ziaee]

Summary

There are a few places where we compare a RELEASE to it's STABLE branch,
or a RELEASE to it's previous release. Use macros so we can bump these
instead of bumping the numbers constantly.

Outstanding:

• I don't know what to do with rel-latest-previous since we're at a .0

currently, it should be whatever the reader should update to before they
update to 15.0. The jails chapter would benefit greatly from that.

• The syntax for escaping to use a macro inside of a code block is

still I can't figure it out... but other than that it's working!

Fixes: ff71b333bffaa8 (releases: define rel-latest macro)

[mhorne]

Thanks for working on these macros. I think in many places they are highly desirable.

shared/releases.adoc

41–42

Right!?

[ziaee]

Hey Mitchell, good to see you. Thanks for looking this over! Fixed yank/put fail, doh!

[mhorne]

The IGNORE seems like a fine solution for now, and can be changed to fit how these macros actually get used. I suspect the active/legacy release lists will still require frequent micro-management. (this is now your purview? ;) )

From my perspective, :rel-latest: is useful for some examples that remain valid over time, but appear stale if they reference the active release at the time of writing, e.g. 12.0.

In D56104#1284795, @ziaee wrote:

Hey Mitchell, good to see you. Thanks for looking this over! Fixed yank/put fail, doh!

:)