Add ability to comment in transport version files (elastic#134329) (elastic#134338)

Comments may be added to the beginning of transport version
files by starting each comment line with the hash # character.

Author: jdconrad

server/src/main/java/org/elasticsearch/TransportVersion.java

@@ -114,7 +114,10 @@ public static TransportVersion fromBufferedReader(
         Integer upperBound
     ) {
         try {
-            String line = bufferedReader.readLine();
+            String line;
+            do {
+                line = bufferedReader.readLine();
+            } while (line.replaceAll("\\s+", "").startsWith("#"));
             String[] parts = line.replaceAll("\\s+", "").split(",");
             String check;
             while ((check = bufferedReader.readLine()) != null) {

server/src/test/java/org/elasticsearch/TransportVersionTests.java

@@ -399,4 +399,41 @@ public void testSupports() {
         assertThat(new TransportVersion(null, 100001000, null).supports(test4), is(true));
         assertThat(new TransportVersion(null, 100001001, null).supports(test4), is(true));
     }
+
+    public void testComment() {
+        byte[] data1 = ("#comment" + System.lineSeparator() + "1000000").getBytes(StandardCharsets.UTF_8);
+        TransportVersion test1 = TransportVersion.fromBufferedReader(
+            "<test>",
+            "testSupports3",
+            false,
+            true,
+            new BufferedReader(new InputStreamReader(new ByteArrayInputStream(data1), StandardCharsets.UTF_8)),
+            5000000
+        );
+        assertThat(new TransportVersion(null, 1000000, null).supports(test1), is(true));
+
+        byte[] data2 = (" # comment" + System.lineSeparator() + "1000000").getBytes(StandardCharsets.UTF_8);
+        TransportVersion test2 = TransportVersion.fromBufferedReader(
+            "<test>",
+            "testSupports3",
+            false,
+            true,
+            new BufferedReader(new InputStreamReader(new ByteArrayInputStream(data2), StandardCharsets.UTF_8)),
+            5000000
+        );
+        assertThat(new TransportVersion(null, 1000000, null).supports(test2), is(true));
+
+        byte[] data3 = ("#comment" + System.lineSeparator() + "# comment3" + System.lineSeparator() + "1000000").getBytes(
+            StandardCharsets.UTF_8
+        );
+        TransportVersion test3 = TransportVersion.fromBufferedReader(
+            "<test>",
+            "testSupports3",
+            false,
+            true,
+            new BufferedReader(new InputStreamReader(new ByteArrayInputStream(data3), StandardCharsets.UTF_8)),
+            5000000
+        );
+        assertThat(new TransportVersion(null, 1000000, null).supports(test3), is(true));
+    }
 }