xref::relative.adoc[] syntax has unexpected meaning
Only a single colon xref: is accepted for the other 7 forms. For the relative-only form, href::relative.adoc[] also works.
The normal meaning of "no module specified" is "ROOT", although that is for a different version and/or component.
Here, however, both the single and double colon xref forms mean "current module", not ROOT.
This ambiguity has certainly confused me.
(I initially did some experiments that seemed to indicate that double-colon xrefs always worked. I don't know how I did that, but my experiments were wrong. I've rewritten the issue.)
Edited by Dan Allen