Bind aggregates over scoped tags to their subtree

CccConventions::TAG_SCOPES maps "update" and "pressemitteilung" to /updates
and "disclosure" to /disclosure. Page.aggregate applies the mapping, so an
aggregate over one of those tags is bounded by its subtree regardless of what
the shortcode says. Tags stay unrestricted; positions are publish-gated.

Both RSS actions call Page.aggregate rather than repeating its tag join.

Empty feeds no longer crash: Atom falls back to the current time for the
required <updated>, and the optional dc:date is omitted.

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/ccc_conventions.rb b/lib/ccc_conventions.rb
index b840dee2..52549c9e 100644
--- a/lib/ccc_conventions.rb
+++ b/lib/ccc_conventions.rb
@@ -52,4 +52,14 @@ module CccConventions
       hint:         "Automatically created under the Chaostreffs overview page, gets tag \"chaostreff-detail\", and uses the chapter detail template."
     }
   }.freeze
+
+  # Tags whose aggregates are forced into a subtree. Editors may apply any
+  # tag anywhere, but a page tagged "update" outside /updates will never
+  # appear in the front-page widget or the RSS feed, because every aggregate
+  # over that tag is scoped here rather than in the shortcode.
+  TAG_SCOPES = {
+    "update"           => "updates",
+    "pressemitteilung" => "updates",
+    "disclosure"       => "disclosure"
+  }.freeze
 end