[IO-870] PathUtils.copyFileToDirectory() across file systems

Simplify

Author: garydgregory

src/changes/changes.xml

@@ -65,6 +65,7 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="fix"                due-to="Gary Gregory">FileChannels.contentEquals(FileChannel, FileChannel, int) can return false when comparing a non-blocking channel.</action>
       <action dev="ggregory" type="fix"                due-to="Gary Gregory">Deprecate FileChannels.contentEquals(FileChannel, FileChannel, int) in favor of FileChannels.contentEquals(SeekableByteChannel, SeekableByteChannel, int).</action>
       <action dev="ggregory" type="fix"                due-to="Gary Gregory">Improve performance of IOUtils.contentEquals(InputStream, InputStream) by about 13%.</action>
+      <action dev="ggregory" type="fix" issue="IO-870" due-to="Gary Gregory">PathUtils.copyFileToDirectory() across file systems #728.</action>
       <!-- ADD -->
       <action dev="ggregory" type="add" issue="IO-860" due-to="Nico Strecker, Gary Gregory">Add ThrottledInputStream.Builder.setMaxBytes(long, ChronoUnit).</action>
       <action dev="ggregory" type="add"                due-to="Gary Gregory">Add IOIterable.</action>

src/main/java/org/apache/commons/io/file/PathUtils.java

@@ -320,12 +320,10 @@ public static Path copyFile(final URL sourceFile, final Path targetFile, final C
      * @throws IOException if an I/O error occurs.
      * @see Files#copy(Path, Path, CopyOption...)
      */
+    @SuppressWarnings("resource") // getFileSystem() is a getter
     public static Path copyFileToDirectory(final Path sourceFile, final Path targetDirectory, final CopyOption... copyOptions) throws IOException {
         // Path.resolve() naturally won't work across FileSystem unless we convert to a String
-        final Path sourceFileName = sourceFile.getFileName();
-        if (sourceFileName == null) {
-            throw new IllegalArgumentException("must have a file name: " + sourceFile);
-        }
+        final Path sourceFileName = Objects.requireNonNull(sourceFile.getFileName(), "source file name");
         final Path targetFile;
         if (sourceFileName.getFileSystem() == targetDirectory.getFileSystem()) {
             targetFile = targetDirectory.resolve(sourceFileName);