Add plugin: redirect_with_metadata #72

Author: yasulab

_plugins/redirect_with_metadata.rb

@@ -0,0 +1,36 @@
+module Jekyll
+  class RedirectWithMetadata < Generator
+    priority :lowest
+
+    def generate(site)
+      redirect_map = build_redirect_map(site)
+
+      redirect_pages = site.pages.select { |page| page.data['redirect'] }
+      redirect_pages.each do |page|
+        target = redirect_map[normalize_url(page.data['redirect']['to'], site)]
+        copy_metadata(from: target, to: page) if target
+      end
+    end
+
+    private
+
+    def build_redirect_map(site)
+      pages_with_redirect_from = (site.pages + site.documents).select { |p| p.data['redirect_from'] }
+      pages_with_redirect_from.flat_map do |page|
+        [page.url, page.data['permalink']].compact.map { |u| [u.chomp('/'), page] }
+      end.to_h
+    end
+
+    def normalize_url(url, site)
+      url.sub(site.config['url'] || '', '')
+         .sub(site.config['baseurl'] || '', '')
+         .chomp('/')
+    end
+
+    def copy_metadata(from:, to:)
+      from.data.each do |key, value|
+        to.data[key] = value unless %w[layout redirect redirect_from permalink].include?(key)
+      end
+    end
+  end
+end