Merge pull request #1664 from fluent/in_tail-fix-tag-with-only-star

in_tail: Fix the error when 'tag *' is configured. fix #1512

lib/fluent/plugin/in_tail.rb

@@ -101,6 +101,7 @@ def configure_parser(conf)
     def configure_tag
       if @tag.index('*')
         @tag_prefix, @tag_suffix = @tag.split('*')
+        @tag_prefix ||= ''
         @tag_suffix ||= ''
       else
         @tag_prefix = nil

test/plugin/test_in_tail.rb

@@ -820,6 +820,18 @@ def test_receive_lines
       engineclass.should_receive(:emit_stream).with('pre.foo.bar.log.post', any).once
       plugin.receive_lines(['foo', 'bar'], DummyWatcher.new('foo.bar.log'))
     end
+
+    config = %[
+      tag *
+      path test/plugin/*/%Y/%m/%Y%m%d-%H%M%S.log,test/plugin/data/log/**/*.log
+      format none
+      read_from_head true
+    ]
+    plugin = create_driver(config, false).instance
+    flexstub(plugin.router) do |engineclass|
+      engineclass.should_receive(:emit_stream).with('foo.bar.log', any).once
+      plugin.receive_lines(['foo', 'bar'], DummyWatcher.new('foo.bar.log'))
+    end
   end
 
   # Ensure that no fatal exception is raised when a file is missing and that