Fixes bug introduced in github issue #132 where renaming a file to itself can cause an unhandled error

lib/streams/DateRollingFileStream.js

@@ -23,10 +23,12 @@ function DateRollingFileStream(filename, pattern, options, now) {
   this.pattern = pattern || '.yyyy-MM-dd';
   this.now = now || Date.now;
   this.lastTimeWeWroteSomething = format.asString(this.pattern, new Date(this.now()));
+  this.alwaysIncludePattern = false;
   this.baseFilename = filename;
     
   if (options) {
     if (options.alwaysIncludePattern) {
+      this.alwaysIncludePattern = true;
       filename = filename + this.lastTimeWeWroteSomething;
     }
     delete options.alwaysIncludePattern;
@@ -75,8 +77,13 @@ DateRollingFileStream.prototype.roll = function(filename, callback) {
     }
 
     function renameTheCurrentFile(cb) {
-        debug("Renaming the " + filename + " -> " + newFilename);
-        fs.rename(filename, newFilename, cb);
+        if (this.alwaysIncludePattern) {
+            // no-op
+            cb();
+        } else {
+            debug("Renaming the " + filename + " -> " + newFilename);
+            fs.rename(filename, newFilename, cb);
+        }
     }
 
 };