Collection relative paths

lib/jekyll/collection.rb

@@ -81,7 +81,7 @@ def filtered_entries
     # Returns a String containing the directory name where the collection
     #   is stored on the filesystem.
     def relative_directory
-      @relative_directory ||= "_#{label}"
+      @relative_directory ||= (metadata['relative_directory'] && site.in_source_dir(metadata['relative_directory']) ||  "_#{label}")
     end
 
     # The full path to the directory containing the collection.

site/_docs/collections.md

@@ -63,6 +63,18 @@ your <code>_config.yml</code> file, with the addition of the preceding <code>_</
   </p>
 </div>
 
+Alternatively, you can place your collection folder wherever you like, and specify the path to this folder in the collection's metadata under `relative_directory`:
+
+{% highlight yaml %}
+collections:
+  my_collection:
+      relative_directory: path/to/my/collection
+{% endhighlight %}
+
+In the above example, the collection would be located at `<source>/path/to/my/collection` instead of `<source>/_my_collection`.
+Note that even though the collection folder is named `collection`, the name of the collection is still that provided in the metadata (`my_collection`).
+The files of the collection are still written out to `<dest>/my_collection/` as before.
+
 ### Step 3: Optionally render your collection's documents into independent files
 
 If you'd like Jekyll to create a public-facing, rendered version of each

test/test_collections.rb

@@ -1,6 +1,37 @@
 require 'helper'
 
 class TestCollections < JekyllUnitTest
+  context "a collection in a subfolder" do
+    setup do
+      @site = fixture_site({
+        "collections" => {
+          "methods" => {
+            "relative_directory" => "_methods/site"
+          }
+        }
+      })
+      @site.process
+      @collection = @site.collections["methods"]
+
+      should "create a collection with label 'methods'" do
+        refute_nil @site.collections["methods"]
+        assert_equal @site.collections["methods"].label, "methods"
+      end
+      should "have a relative path equal to that in the metadata" do
+        assert_equal @collection.relative_directory, "_methods/site"
+      end
+      should "be a collection of the files in the relative directory" do
+        assert_equal 2, @collection.docs.size
+        @site.collections["methods"].docs.each do |doc|
+          assert_includes %w[
+            _methods/site/generate.md
+            _methods/site/initialize.md
+          ], doc.relative_path
+        end
+      end
+    end
+  end
+
   context "an evil collection" do
     setup do
       @collection = Jekyll::Collection.new(fixture_site, "../../etc/password")