bug fix: silently fails overwriting symlinks

When A is an existing symlink to B, then createSymbolicLink(A,C) does
neither overwrite A->B by A->C (as expected in analogy to the behavior
of copy(A,C)) nor does it throw an exception nor does it return A->B to
indicate the failure, but it actually "silently fails", i. e. it returns
A->C!

This certainly is heavily problematic, unsymmetric to what
copy(File,File) and Files.createSymbolicLink(Path,Path) do, and
certainly unwanted and buggy behavior.

The solution is to delete any existing target before creating the
symlic, hence copying the behavior of copy(File,File).

Author: mkarg

src/main/java/org/codehaus/plexus/util/NioFiles.java

@@ -120,10 +120,11 @@ public static File createSymbolicLink( File symlink, File target )
         throws IOException
     {
         Path link = symlink.toPath();
-        if ( !Files.exists( link, LinkOption.NOFOLLOW_LINKS ) )
+        if ( Files.exists( link, LinkOption.NOFOLLOW_LINKS ) )
         {
-            link = Files.createSymbolicLink( link, target.toPath() );
+            Files.delete( link );
         }
+        link = Files.createSymbolicLink( link, target.toPath() );
         return link.toFile();
     }
 
@@ -144,4 +145,4 @@ public static File copy( File source, File target )
     }
 
 
-}
+}