add support for categories frontmatter

lib/jekyll-feed/generator.rb

@@ -86,7 +86,7 @@ def generate_tag_feed(tags_pool, tags_path)
       tags_pool.each do |tag|
         # allow only tags with basic alphanumeric characters and underscore to keep
         # feed path simple.
-        next if tag =~ %r![^a-zA-Z0-9_]!
+        next if %r![^a-zA-Z0-9_]!.match?(tag)
 
         Jekyll.logger.info "Jekyll Feed:", "Generating feed for posts tagged #{tag}"
         path = "#{tags_path}#{tag}.xml"

spec/fixtures/_posts/2014-03-02-march-the-second.md

@@ -1,8 +1,6 @@
 ---
 image: https://cdn.example.org/absolute.png?h=188&w=250
 category: news
-tags:
- - test
 ---
 
 March the second!

spec/fixtures/_posts/2015-05-12-liquid.md

@@ -1,4 +1,5 @@
 ---
+categories: [first, second, third]
 ---
 
 {% capture liquidstring %}

spec/jekyll-feed_spec.rb

@@ -316,6 +316,19 @@
     end
   end
 
+  context "with 'categories' or 'category' or 'tags' key in the front matter" do
+    let(:feed) { RSS::Parser.parse(contents) }
+    let(:entry_with_single_category) { feed.items.find { |i| i.title.content == "March The Second" } }
+    let(:entry_with_multiple_categories) { feed.items.find { |i| i.title.content == "Liquid" } }
+    let(:entry_with_multiple_categories_and_tags) { feed.items.find { |i| i.title.content == "Sparkling Title" } }
+
+    it "generates the feed correctly" do
+      expect(entry_with_single_category.categories.map(&:term)).to eql(%w(news))
+      expect(entry_with_multiple_categories.categories.map(&:term)).to eql(%w(first second third))
+      expect(entry_with_multiple_categories_and_tags.categories.map(&:term)).to eql(["updates", "jekyll", "\"/><VADER>", "test"])
+    end
+  end
+
   context "changing the file path via collection meta" do
     let(:overrides) do
       {
@@ -526,7 +539,6 @@
         expect(Pathname.new(dest_dir("feed/by_tag/success.xml"))).to exist
 
         expect(tags_feed_test).to match "/2013/12/12/dec-the-second.html"
-        expect(tags_feed_test).to match "/2014/03/02/march-the-second.html"
         expect(tags_feed_test).to match "/2014/03/04/march-the-fourth.html"
         expect(tags_feed_test).to match "/2015/01/18/jekyll-last-modified-at.html"
         expect(tags_feed_test).to match "/2015/05/12/pre.html"