Warn when registering external static folder

[main] WARN spark.staticfiles.StaticFilesFolder - Registering external static files folder [/Users/USERNAME/AppData/Local/Temp/external/] as [C:/Users/USERNAME/AppData/Local/Temp/external].

[main] WARN spark.staticfiles.StaticFilesFolder - Registering external static files folder [c:/Users/USERNAME/AppData/Local/Temp/external/] as [c:/Users/USERNAME/AppData/Local/Temp/external].

[main] WARN spark.staticfiles.StaticFilesFolder - Registering external static files folder [C:\Users\USERNAME\AppData\Local\Temp\external\] as [C:/Users/USERNAME/AppData/Local/Temp/external].

src/main/java/spark/staticfiles/StaticFilesFolder.java

@@ -1,13 +1,18 @@
 package spark.staticfiles;
 
-import static spark.utils.StringUtils.removeLeadingAndTrailingSlashesFrom;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.nio.file.Paths;
 
+import static spark.utils.StringUtils.removeLeadingAndTrailingSlashesFrom;
+
 /**
  * Created by Per Wendel on 2016-11-05.
  */
 public class StaticFilesFolder {
-
+    private static final Logger LOG = LoggerFactory.getLogger(StaticFilesFolder.class);
+
     private static volatile String local;
     private static volatile String external;
 
@@ -17,10 +22,10 @@ public static final void localConfiguredTo(String folder) {
     }
 
     public static final void externalConfiguredTo(String folder) {
-        
-        external = removeLeadingAndTrailingSlashesFrom(
-            Paths.get(folder).toAbsolutePath().toString().replace("\\", "/")
-        );
+
+        String unixLikeFolder = Paths.get(folder).toAbsolutePath().toString().replace("\\", "/");
+        LOG.warn("Registering external static files folder [{}] as [{}].", folder, unixLikeFolder);
+        external = removeLeadingAndTrailingSlashesFrom(unixLikeFolder);
     }
 
     public static final String local() {
@@ -31,5 +36,4 @@ public static final String external() {
         return external;
     }
 
-
 }