fix logfile opening to be sensible

OpenRA.FileFormats/Support/Log.cs

@@ -34,32 +34,37 @@ namespace OpenRA
 			set
 			{
 				LogPathPrefix = value;				
-				if (!Directory.Exists(LogPathPrefix))
 				Directory.CreateDirectory(LogPathPrefix);
 			}
 		}
 
-		public static void AddChannel(string channelName, string filename)
+        static IEnumerable<string> FilenamesForChannel(string channelName, string baseFilename)
+        {
+            for(var i = 0;; i++ )
+                yield return Path.Combine(LogPathPrefix, 
+                    i > 0 ? "{0}.{1}".F(baseFilename, i) : baseFilename);
+        }
+
+        public static void AddChannel(string channelName, string baseFilename)
         {
             if (channels.ContainsKey(channelName)) return;
 
-			var i = 0;
-			var f = filename;
-			while (File.Exists(LogPathPrefix + filename))
+            foreach (var filename in FilenamesForChannel(channelName, baseFilename))
                 try
                 {
-					StreamWriter writer = File.CreateText(LogPathPrefix + filename);
+                    var writer = File.CreateText(filename);
                     writer.AutoFlush = true;
-					channels.Add(channelName, new ChannelInfo() { Filename = filename, Writer = writer });
+
+                    channels.Add(channelName,
+                        new ChannelInfo()
+                        {
+                            Filename = filename,
+                            Writer = writer
+                        });
+
                     return;
                 }
-				catch (IOException) { filename = f + ".{0}".F(++i); }
-			
-			//if no logs exist, just make it
-			StreamWriter w = File.CreateText(LogPathPrefix + filename);
-			w.AutoFlush = true;
-			channels.Add(channelName, new ChannelInfo() { Filename = filename, Writer = w });
-			
+                catch (IOException) { }
         }
 
 		public static void Write(string channel, string format, params object[] args)