Add constants for parsing git wire protocol version

This would allow other JGit users to access and reuse the constants.

Change-Id: I1608802f45586af5f8582afa592e26679e9cebe3
Signed-off-by: David Ostrovsky <david@ostrovsky.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/HttpClientTests.java

 import org.eclipse.jgit.junit.TestRepository;
 import org.eclipse.jgit.junit.http.AccessEvent;
 import org.eclipse.jgit.junit.http.AppServer;
+import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.transport.PacketLineIn;
 import org.eclipse.jgit.transport.PacketLineOut;
 import org.eclipse.jgit.transport.Transport;
+import org.eclipse.jgit.transport.TransferConfig;
 import org.eclipse.jgit.transport.URIish;
 import org.eclipse.jgit.transport.UsernamePasswordCredentialsProvider;
 import org.eclipse.jgit.transport.http.HttpConnection;
 
 	@Test
 	public void testV2HttpFirstResponse() throws Exception {
-		remoteRepository.getRepository().getConfig().setInt(
-				"protocol", null, "version", 2);
+		remoteRepository.getRepository().getConfig().setString(
+				ConfigConstants.CONFIG_PROTOCOL_SECTION, null,
+				ConfigConstants.CONFIG_KEY_VERSION,
+				TransferConfig.ProtocolVersion.V2.version());
 
 		String url = smartAuthNoneURI.toString() + "/info/refs?service=git-upload-pack";
 		HttpConnection c = HttpTransport.getConnectionFactory()
 
 	@Test
 	public void testV2HttpSubsequentResponse() throws Exception {
-		remoteRepository.getRepository().getConfig().setInt(
-				"protocol", null, "version", 2);
+		remoteRepository.getRepository().getConfig().setString(
+				ConfigConstants.CONFIG_PROTOCOL_SECTION, null,
+				ConfigConstants.CONFIG_KEY_VERSION,
+				TransferConfig.ProtocolVersion.V2.version());
 
 		String url = smartAuthNoneURI.toString() + "/git-upload-pack";
 		HttpConnection c = HttpTransport.getConnectionFactory()

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/UploadPackTest.java

 import org.eclipse.jgit.internal.storage.pack.CachedPack;
 import org.eclipse.jgit.internal.storage.pack.CachedPackUriProvider;
 import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.NullProgressMonitor;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
 
 		ByteArrayInputStream send = linesAsInputStream(inputLines);
 
-		server.getConfig().setString("protocol", null, "version", "2");
+		server.getConfig().setString(ConfigConstants.CONFIG_PROTOCOL_SECTION,
+				null, ConfigConstants.CONFIG_KEY_VERSION,
+				TransferConfig.ProtocolVersion.V2.version());
 		UploadPack up = new UploadPack(server);
 		if (postConstructionSetup != null) {
 			postConstructionSetup.accept(up);
 
 	@Test
 	public void testGetPeerAgentProtocolV2() throws Exception {
-		server.getConfig().setString("protocol", null, "version", "2");
+		server.getConfig().setString(ConfigConstants.CONFIG_PROTOCOL_SECTION,
+				null, ConfigConstants.CONFIG_KEY_VERSION,
+				TransferConfig.ProtocolVersion.V2.version());
 
 		RevCommit one = remote.commit().message("1").create();
 		remote.update("one", one);

org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java

 	 */
 	public static final String CONFIG_GPG_SECTION = "gpg";
 
+	/**
+	 * The "protocol" section
+	 * @since 5.9
+	 */
+	public static final String CONFIG_PROTOCOL_SECTION = "protocol";
+
 	/**
 	 * The "format" key
 	 * @since 5.2
 	public static final String CONFIG_INDEX_SECTION = "index";
 
 	/**
-	 * The "index.version" key
+	 * The "version" key
 	 *
 	 * @since 5.9
 	 */

org.eclipse.jgit/src/org/eclipse/jgit/transport/TransferConfig.java

 import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.internal.storage.file.LazyObjectIdSetFile;
 import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Config.SectionParser;
 import org.eclipse.jgit.lib.ObjectChecker;
 import org.eclipse.jgit.lib.ObjectIdSet;
 	}
 
 	/**
-	 * A git configuration variable for which versions of the Git protocol to prefer.
-	 * Used in protocol.version.
+	 * A git configuration variable for which versions of the Git protocol to
+	 * prefer. Used in protocol.version.
+	 *
+	 * @since 5.9
 	 */
-	enum ProtocolVersion {
+	public enum ProtocolVersion {
+		/**
+		 * Git wire protocol version 0 (the default).
+		 */
 		V0("0"), //$NON-NLS-1$
+		/**
+		 * Git wire protocol version 2.
+		 */
 		V2("2"); //$NON-NLS-1$
 
 		final String name;
 			this.name = name;
 		}
 
+		/**
+		 * Returns version number
+		 *
+		 * @return string version
+		 */
+		public String version() {
+			return name;
+		}
+
 		@Nullable
 		static ProtocolVersion parse(@Nullable String name) {
 			if (name == null) {
 				"uploadpack", "allowreachablesha1inwant", false);
 		allowFilter = rc.getBoolean(
 				"uploadpack", "allowfilter", false);
-		protocolVersion = ProtocolVersion.parse(rc.getString("protocol", null, "version"));
+		protocolVersion = ProtocolVersion.parse(rc
+				.getString(ConfigConstants.CONFIG_PROTOCOL_SECTION, null,
+						ConfigConstants.CONFIG_KEY_VERSION));
 		hideRefs = rc.getStringList("uploadpack", null, "hiderefs");
 		allowSidebandAll = rc.getBoolean(
 				"uploadpack", "allowsidebandall", false);