If you say

    pagespec_match_list($page, $spec, list => \@pages)

with a small list `@pages` and a vague pagespec `$spec`, `$page` ends
up depending on (every page that matches) `$spec`. For instance, if you
already have a list of subpages of the sandbox, and you want to filter it
to only the discussion pages, you can do that like

    pagespec_match_list("sandbox", "*/discussion",
        list => ["sandbox/discussion", "sandbox/things", "sandbox/stuff"])

but then a change to *any* discussion page will refresh the sandbox.

The [[bugs/trails depend on everything]] bug was a particularly bad
case of this, with the widest possible pagespec `internal(*)`
matched against a small list (the trail).

In principle it would be nice if `pagespec_match_list` could detect
this situation and make sandbox depend on only those subpages instead.

Perhaps if the `list` parameter is given, `p_m_l` should add a
by-name (simple) dependency on each page in that list, instead
of a dependency on the pagespec? Or perhaps it should be documented
that plugins can pass `deptype => 0` to take responsibility for
their own dependency handling, and then do whatever they need?

Uses of `pagespec_match_list` with a non-trivial list, in-tree,
after [[bugs/trails depend on everything]] is fixed:

* brokenlinks: really does need to depend on the whole pagespec,
  but that could be done separately

* inline: the inliner already depends on the inlined pages
  so no extra dependency is needed

* pagestats: same as brokenlinks

My album plugin is in the same situation as inline.

--[[smcv]]