[CLI-287] Allow whitespace-only header and footer (apache#26)

* [CLI-287] Allow whitespace-only header and footer

* [CLI-287] Add tests

Author: MrQubo

src/main/java/org/apache/commons/cli/HelpFormatter.java

@@ -482,13 +482,13 @@ public void printHelp(final PrintWriter pw, final int width, final String cmdLin
             printUsage(pw, width, cmdLineSyntax);
         }
 
-        if (header != null && !header.trim().isEmpty()) {
+        if (header != null && !header.isEmpty()) {
             printWrapped(pw, width, header);
         }
 
         printOptions(pw, width, options, leftPad, descPad);
 
-        if (footer != null && !footer.trim().isEmpty()) {
+        if (footer != null && !footer.isEmpty()) {
             printWrapped(pw, width, footer);
         }
     }

src/test/java/org/apache/commons/cli/HelpFormatterTest.java

@@ -293,6 +293,62 @@ public void testOptionWithoutShortFormat2() {
         //@formatter:on
     }
 
+    @Test
+    public void testPrintHelpNewlineFooter()
+    {
+        final HelpFormatter formatter = new HelpFormatter();
+        final ByteArrayOutputStream out = new ByteArrayOutputStream();
+        final PrintWriter pw = new PrintWriter(out);
+
+        final Options options = new Options();
+        options.addOption("a", "b");
+
+        formatter.printHelp(
+            pw,
+            80,
+            "test" + EOL,
+            "header" + EOL,
+            options,
+            0,
+            0,
+            EOL
+        );
+        final String expected = "usage: test" + EOL +
+                          "header" + EOL +
+                          "-ab" + EOL +
+                          EOL;
+        pw.flush();
+        assertEquals("footer newline", expected, out.toString());
+    }
+
+    @Test
+    public void testPrintHelpNewlineHeader()
+    {
+        final HelpFormatter formatter = new HelpFormatter();
+        final ByteArrayOutputStream out = new ByteArrayOutputStream();
+        final PrintWriter pw = new PrintWriter(out);
+
+        final Options options = new Options();
+        options.addOption("a", "b");
+
+        formatter.printHelp(
+            pw,
+            80,
+            "test" + EOL,
+            EOL,
+            options,
+            0,
+            0,
+            "footer" + EOL
+        );
+        String expected = "usage: test" + EOL +
+                          EOL +
+                          "-ab" + EOL +
+                          "footer" + EOL;
+        pw.flush();
+        assertEquals("header newline", expected, out.toString());
+    }
+
     @Test
     public void testPrintHelpWithEmptySyntax() {
         final HelpFormatter formatter = new HelpFormatter();