daemon: Add --ketch=LEADER flag

Experimental flag to turn on the KetchLeader within this daemon JVM.
This is a manually elected leader process, set from the command line.
Remote followers for each repository are configured per-repository
using remote sections with ketch-type = FULL. For example:

Manually elected leader's $GIT_DIR/config:

  [ketch]
    name = A

  [remote "A"]
    ketch-type = FULL

  [remote "B"]
    url = git://127.0.0.1:9421/sample.git
    ketch-type = FULL

  [remote "C"]
    url = git://127.0.0.1:9422/sample.git
    ketch-type = FULL

Replica B and C daemons:

  git daemon \
    --export-all \
    --enable=receive-pack \
    --listen=127.0.0.1 --port=9421 \
    --base-path=$HOME/ketch_test/follower_one \
    $HOME/ketch_test/follower_one &

  git daemon \
    --export-all \
    --enable=receive-pack \
    --listen=127.0.0.1 --port=9422 \
    --base-path=$HOME/ketch_test/follower_two \
    $HOME/ketch_test/follower_two &

Change-Id: I165f85970a77e16b5263115290d685d8a00566f5

org.eclipse.jgit.pgm/META-INF/MANIFEST.MF

@@ -19,6 +19,7 @@ Import-Package: org.apache.commons.compress.archivers;version="[1.3,2.0)",
  org.eclipse.jgit.dircache;version="[4.2.0,4.3.0)",
  org.eclipse.jgit.errors;version="[4.2.0,4.3.0)",
  org.eclipse.jgit.gitrepo;version="[4.2.0,4.3.0)",
+ org.eclipse.jgit.internal.ketch;version="[4.2.0,4.3.0)",
  org.eclipse.jgit.internal.storage.file;version="[4.2.0,4.3.0)",
  org.eclipse.jgit.internal.storage.pack;version="[4.2.0,4.3.0)",
  org.eclipse.jgit.internal.storage.reftree;version="[4.2.0,4.3.0)",

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Daemon.java

@@ -45,18 +45,29 @@ package org.eclipse.jgit.pgm;
 
 import java.io.File;
 import java.net.InetSocketAddress;
+import java.net.URISyntaxException;
 import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.Executors;
 
+import org.eclipse.jgit.internal.ketch.KetchLeader;
+import org.eclipse.jgit.internal.ketch.KetchLeaderCache;
+import org.eclipse.jgit.internal.ketch.KetchPreReceive;
+import org.eclipse.jgit.internal.ketch.KetchSystem;
+import org.eclipse.jgit.internal.ketch.KetchText;
+import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.pgm.internal.CLIText;
 import org.eclipse.jgit.storage.file.FileBasedConfig;
 import org.eclipse.jgit.storage.file.WindowCacheConfig;
 import org.eclipse.jgit.storage.pack.PackConfig;
 import org.eclipse.jgit.transport.DaemonClient;
 import org.eclipse.jgit.transport.DaemonService;
+import org.eclipse.jgit.transport.ReceivePack;
 import org.eclipse.jgit.transport.resolver.FileResolver;
+import org.eclipse.jgit.transport.resolver.ReceivePackFactory;
+import org.eclipse.jgit.transport.resolver.ServiceNotAuthorizedException;
+import org.eclipse.jgit.transport.resolver.ServiceNotEnabledException;
 import org.eclipse.jgit.util.FS;
 import org.kohsuke.args4j.Argument;
 import org.kohsuke.args4j.Option;
@@ -90,6 +101,13 @@ class Daemon extends TextBuiltin {
 	@Option(name = "--export-all", usage = "usage_exportWithoutGitDaemonExportOk")
 	boolean exportAll;
 
+	@Option(name = "--ketch")
+	KetchServerType ketchServerType;
+
+	enum KetchServerType {
+		LEADER;
+	}
+
 	@Argument(required = true, metaVar = "metaVar_directory", usage = "usage_directoriesToExport")
 	final List<File> directory = new ArrayList<File>();
 
@@ -146,7 +164,9 @@ class Daemon extends TextBuiltin {
 			service(d, n).setOverridable(true);
 		for (final String n : forbidOverride)
 			service(d, n).setOverridable(false);
-
+		if (ketchServerType == KetchServerType.LEADER) {
+			startKetchLeader(d);
+		}
 		d.start();
 		outw.println(MessageFormat.format(CLIText.get().listeningOn, d.getAddress()));
 	}
@@ -159,4 +179,29 @@ class Daemon extends TextBuiltin {
 			throw die(MessageFormat.format(CLIText.get().serviceNotSupported, n));
 		return svc;
 	}
+
+	private void startKetchLeader(org.eclipse.jgit.transport.Daemon daemon) {
+		KetchSystem system = new KetchSystem();
+		final KetchLeaderCache leaders = new KetchLeaderCache(system);
+		final ReceivePackFactory<DaemonClient> factory;
+
+		factory = daemon.getReceivePackFactory();
+		daemon.setReceivePackFactory(new ReceivePackFactory<DaemonClient>() {
+			@Override
+			public ReceivePack create(DaemonClient req, Repository repo)
+					throws ServiceNotEnabledException,
+					ServiceNotAuthorizedException {
+				ReceivePack rp = factory.create(req, repo);
+				KetchLeader leader;
+				try {
+					leader = leaders.get(repo);
+				} catch (URISyntaxException err) {
+					throw new ServiceNotEnabledException(
+							KetchText.get().invalidFollowerUri, err);
+				}
+				rp.setPreReceiveHook(new KetchPreReceive(leader));
+				return rp;
+			}
+		});
+	}
 }

org.eclipse.jgit/resources/org/eclipse/jgit/internal/ketch/KetchText.properties

@@ -1,6 +1,7 @@
 accepted=accepted.
 cannotFetchFromLocalReplica=cannot fetch from LocalReplica
 failed=failed!
+invalidFollowerUri=invalid follower URI
 leaderFailedToStore=leader failed to store
 localReplicaRequired=LocalReplica instance is required
 mismatchedTxnNamespace=mismatched txnNamespace; expected {0} found {1}

org.eclipse.jgit/src/org/eclipse/jgit/internal/ketch/KetchText.java

@@ -57,6 +57,7 @@ public class KetchText extends TranslationBundle {
 	/***/ public String accepted;
 	/***/ public String cannotFetchFromLocalReplica;
 	/***/ public String failed;
+	/***/ public String invalidFollowerUri;
 	/***/ public String leaderFailedToStore;
 	/***/ public String localReplicaRequired;
 	/***/ public String mismatchedTxnNamespace;

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

@@ -255,6 +255,16 @@ public class Daemon {
 			uploadPackFactory = (UploadPackFactory<DaemonClient>) UploadPackFactory.DISABLED;
 	}
 
+	/**
+	 * Get the factory used to construct per-request ReceivePack.
+	 *
+	 * @return the factory.
+	 * @since 4.2
+	 */
+	public ReceivePackFactory<DaemonClient> getReceivePackFactory() {
+		return receivePackFactory;
+	}
+
 	/**
 	 * Set the factory to construct and configure per-request ReceivePack.
 	 *