Refactoring Tar: extract getCanonicalPrefix()

src/main/org/apache/tools/ant/taskdefs/Tar.java

@@ -405,12 +405,7 @@ public class Tar extends MatchingTask {
                     return;
                 }
 
-                String prefix = tarFileSet.getPrefix(this.getProject());
-                // '/' is appended for compatibility with the zip task.
-                if (!prefix.isEmpty() && !prefix.endsWith("/")) {
-                    prefix += "/";
-                }
-                vPath = prefix + vPath;
+                vPath = getCanonicalPrefix(tarFileSet, this.getProject()) + vPath;
             } else {
                 vPath = fullpath;
             }
@@ -785,6 +780,15 @@ public class Tar extends MatchingTask {
         return tfs;
     }
 
+    private static String getCanonicalPrefix(TarFileSet tarFileSet, Project project) {
+        String prefix = tarFileSet.getPrefix(project);
+        // '/' is appended for compatibility with the zip task.
+        if (prefix.isEmpty() || prefix.endsWith("/")) {
+            return prefix;
+        }
+        return prefix += "/";
+    }
+
     /**
      * This is a FileSet with the option to specify permissions
      * and other attributes.