Add Utils.safe_glob method

which works the same way as Dir.glob but seperating the input
into two parts ('dir' + '/' + 'pattern') to make sure
the first part('dir') does not act as a pattern.

lib/jekyll/utils.rb

@@ -207,5 +207,34 @@ module Jekyll
       template
     end
 
+
+    # Work the same way as Dir.glob but seperating the input into two parts
+    # ('dir' + '/' + 'pattern') to make sure the first part('dir') does not act
+    # as a pattern.
+    #
+    # For example, Dir.glob("path[/*") always returns an empty array,
+    # because the method fails to find the closing pattern to '[' which is ']'
+    #
+    # Examples:
+    #   safe_glob("path[", "*")
+    #   # => ["path[/file1", "path[/file2"]
+    #
+    #   safe_glob("path", "*", File::FNM_DOTMATCH)
+    #   # => ["path/.", "path/..", "path/file1"]
+    #
+    # dir     - the dir where glob will be executed under
+    #           (the dir will be included to each result)
+    # pattern - the pattern which will be applied under the dir
+    # flags   - the flags which will be applied to the pattern
+    #
+    # Returns matched pathes
+    def safe_glob(dir, pattern, flags = 0)
+      return [] unless Dir.exist?(dir)
+      return [dir] if pattern.nil? || pattern.empty?
+      Dir.chdir(dir) do
+        Dir.glob(pattern, flags).map { |f| File.join(dir, f) }
+      end
+    end
+
   end
 end

test/test_utils.rb

@@ -180,4 +180,38 @@ class TestUtils < JekyllUnitTest
       assert_equal "/:basename", Utils.add_permalink_suffix("/:basename", "/:title")
     end
   end
+
+  context "The \`Utils.safe_glob\` method" do
+    should "not apply pattern to the dir" do
+      dir = "test/safe_glob_test["
+      assert_equal [], Dir.glob(dir + "/*")
+      assert_equal ["test/safe_glob_test[/find_me.txt"], Utils.safe_glob(dir, "*")
+    end
+
+    should "return the same data to #glob" do
+      dir = "test"
+      assert_equal Dir.glob(dir + "/*"), Utils.safe_glob(dir, "*")
+      assert_equal Dir.glob(dir + "/**/*"), Utils.safe_glob(dir, "**/*")
+    end
+
+    should "return the same data to #glob if dir is not found" do
+      dir = "dir_not_exist"
+      assert_equal [], Utils.safe_glob(dir, "*")
+      assert_equal Dir.glob(dir + "/*"), Utils.safe_glob(dir, "*")
+    end
+
+    should "return the same data to #glob if pattern is blank" do
+      dir = "test"
+      assert_equal [dir], Utils.safe_glob(dir, "")
+      assert_equal Dir.glob(dir), Utils.safe_glob(dir, "")
+      assert_equal Dir.glob(dir), Utils.safe_glob(dir, nil)
+    end
+
+    should "return the same data to #glob if flag is given" do
+      dir = "test"
+      assert_equal Dir.glob(dir + "/*", File::FNM_DOTMATCH),
+                   Utils.safe_glob(dir, "*", File::FNM_DOTMATCH)
+    end
+  end
+
 end