Declare canonical URL

Author: mrotteveel

doc-extension.groovy

@@ -1,7 +1,7 @@
 // Preprocessor for since/until roles in pdf backend (in html5 backed this is handled using CSS)
 preprocessor {
     document, reader ->
-        if (document.options['backend'] != 'pdf') {
+        if (!document.basebackend('pdf')) {
             println 'skipping since/until preprocessor for non-PDF'
             return
         }
@@ -26,4 +26,12 @@ preprocessor {
             }
         }
         reader.restoreLines(replacement)
+}
+docinfo_processor {
+    document -> {
+        if (!document.basebackend('html') || !document.hasAttribute('fb-canonical-html')) {
+            return
+        }
+        return "<link rel=\"canonical\" href=\"${document.getAttribute('fb-canonical-html')}\"/>"
+    }
 }

src/docs/asciidoc/jaybird_manual.adoc

@@ -26,6 +26,7 @@ Roman Rokytskyy; Mark Rotteveel
 :jaybird-template-version: {jaybird5-template-version}
 :jna-version: 5.14.0
 :min-support-firebird: 2.5
+:fb-canonical-html: https://firebirdsql.github.io/jaybird-manual/jaybird_manual.html
 :is-snapshot:
 
 ifdef::is-snapshot[]