merge with master

src/compiler/commandLineParser.ts

@@ -468,6 +468,9 @@ namespace ts {
                             }
                             if (opt.isFilePath) {
                                 value = normalizePath(combinePaths(basePath, value));
+                                if (value === "") {
+                                    value = ".";
+                                }
                             }
                             options[opt.name] = value;
                         }
@@ -517,4 +520,4 @@ namespace ts {
             return fileNames;
         }
     }
-}
+}