[API] Added the "Search Shards" API

Related: elastic/elasticsearch#5907

See: http://www.elasticsearch.org/guide/en/elasticsearch/reference/master/search-shards.html

elasticsearch-api/lib/elasticsearch/api/actions/search_shards.rb

@@ -0,0 +1,41 @@
+module Elasticsearch
+  module API
+    module Actions
+
+      # Returns the names of indices and shards on which a search request would be executed
+      #
+      # @option arguments [String] :index The name of the index
+      # @option arguments [String] :type The type of the document
+      # @option arguments [String] :preference Specify the node or shard the operation should be performed on
+      #                                        (default: random)
+      # @option arguments [String] :routing Specific routing value
+      # @option arguments [Boolean] :local Return local information, do not retrieve the state from master node
+      #                                    (default: false)
+      # @option arguments [Boolean] :ignore_unavailable Whether specified concrete indices should be ignored when
+      #                                                 unavailable (missing or closed)
+      # @option arguments [Boolean] :allow_no_indices Whether to ignore if a wildcard indices expression resolves
+      #                                               into no concrete indices.
+      #                                               (This includes `_all` or when no indices have been specified)
+      # @option arguments [String] :expand_wildcards Whether to expand wildcard expression to concrete indices
+      #                                              that are open, closed or both. (options: open, closed)
+      #
+      # @see http://www.elasticsearch.org/guide/en/elasticsearch/reference/master/search-shards.html
+      #
+      def search_shards(arguments={})
+        valid_params = [
+          :preference,
+          :routing,
+          :local,
+          :ignore_unavailable,
+          :allow_no_indices,
+          :expand_wildcards ]
+        method = 'GET'
+        path   = Utils.__pathify( Utils.__listify(arguments[:index]), Utils.__listify(arguments[:type]), '_search_shards' )
+        params = Utils.__validate_and_extract_params arguments, valid_params
+        body   = nil
+
+        perform_request(method, path, params, body).body
+      end
+    end
+  end
+end

elasticsearch-api/test/unit/search_shards_test.rb

@@ -0,0 +1,26 @@
+require 'test_helper'
+
+module Elasticsearch
+  module Test
+    class SearchShardsTest < ::Test::Unit::TestCase
+
+      context "Search shards" do
+        subject { FakeClient.new }
+
+        should "perform correct request" do
+          subject.expects(:perform_request).with do |method, url, params, body|
+            assert_equal 'GET', method
+            assert_equal '_search_shards', url
+            assert_equal Hash.new, params
+            assert_nil   body
+            true
+          end.returns(FakeResponse.new)
+
+          subject.search_shards
+        end
+
+      end
+
+    end
+  end
+end