Implement `file_match' condition keyword

lib/producer/core/condition.rb

@@ -36,6 +36,7 @@ module Producer
       define_test :sh,              Tests::ShellCommandStatus
       define_test :file_contains,   Tests::FileContains
       define_test :file_eq,         Tests::FileEq
+      define_test :file_match,      Tests::FileMatch
       define_test :env?,            Tests::HasEnv
       define_test :executable?,     Tests::HasExecutable
       define_test :dir?,            Tests::HasDir

lib/producer/core/tests/file_match.rb

@@ -0,0 +1,18 @@
+module Producer
+  module Core
+    module Tests
+      class FileMatch < Test
+        def verify
+          !!(file_content =~ arguments[1])
+        end
+
+
+        private
+
+        def file_content
+          fs.file_read(arguments[0]) or ''
+        end
+      end
+    end
+  end
+end