Enable full Transport configuration for JGit API commands

Add a TransportConfigCallback parameter to JGit API commands, to allow
consumers of the JGit command API to perform custom Transport configuration
that would be otherwise difficult to anticipate & expose on the API command
builders.


My specific use-case is configuring additional properties on SshTransport
- I need to take over the SshSessionFactory used by the transport. Using
TransportConfigCallback I can simply do this (rather than reimplement the
API command classes):

public void configure(Transport tn) {
  if (tn instanceof SshTransport) {
    ((SshTransport) tn).setSshSessionFactory(factoryProvider.get());
  }
}

Adding an explicit setSshSessionFactory() method to the JGit command
classes would bloat the API. Also, creating the replacement
SshSessionFactory is unnecessary if the transport is not SSH, but the type
of the Transport is only known once the remote has been resolved and the
URI parsed - consequently it makes sense to perform this step in a
callback, where the transport instance can be inspected to determine if
it's of a relevant type.


A note about where this leaves the API - there are now 4 commands:

CloneCommand
PullCommand
FetchCommand
PushCommand

-that share 3 identical transport-related parameters:

timeout
credentialsProvider
transportConfigurator

I think there's potential for introducing an interface or val-object to
identify/encapsulate this repetition, which I'd be happy to do in a
subsequent commit.

Change-Id: I8983c3627cdd7d7b2aeb0b6a3dadee553378b951
Signed-off-by: Roberto Tyley <roberto.tyley@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/api/CloneCommand.java

@@ -104,6 +104,8 @@ public class CloneCommand implements Callable<Git> {
 
 	private Collection<String> branchesToClone;
 
+	private TransportConfigCallback transportConfigCallback;
+
 	/**
 	 * Executes the {@code Clone} command.
 	 *
@@ -167,6 +169,7 @@ public class CloneCommand implements Callable<Git> {
 		command.setTimeout(timeout);
 		if (credentialsProvider != null)
 			command.setCredentialsProvider(credentialsProvider);
+		command.setTransportConfigCallback(transportConfigCallback);
 
 		List<RefSpec> specs = calculateRefSpecs(dst);
 		command.setRefSpecs(specs);
@@ -394,4 +397,17 @@ public class CloneCommand implements Callable<Git> {
 		return this;
 	}
 
+	/**
+	 * @param transportConfigCallback
+	 *            if set, the callback will be invoked after the Transport has
+	 *            created, but before the Transport is used. The callback can
+	 *            use this opportunity to set additional type-specific
+	 *            configuration on the Transport instance.
+	 * @return {@code this}
+	 */
+	public CloneCommand setTransportConfigCallback(
+			TransportConfigCallback transportConfigCallback) {
+		this.transportConfigCallback = transportConfigCallback;
+		return this;
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/api/FetchCommand.java

@@ -93,6 +93,8 @@ public class FetchCommand extends GitCommand<FetchResult> {
 
 	private TagOpt tagOption;
 
+	private TransportConfigCallback transportConfigCallback;
+
 	/**
 	 * @param repo
 	 */
@@ -132,6 +134,8 @@ public class FetchCommand extends GitCommand<FetchResult> {
 				transport.setFetchThin(thin);
 				if (credentialsProvider != null)
 					transport.setCredentialsProvider(credentialsProvider);
+				if (transportConfigCallback != null)
+					transportConfigCallback.configure(transport);
 
 				FetchResult result = transport.fetch(monitor, refSpecs);
 				return result;
@@ -353,4 +357,19 @@ public class FetchCommand extends GitCommand<FetchResult> {
 		this.tagOption = tagOpt;
 		return this;
 	}
+
+	/**
+	 * @param transportConfigCallback
+	 *            if set, the callback will be invoked after the Transport has
+	 *            created, but before the Transport is used. The callback can
+	 *            use this opportunity to set additional type-specific
+	 *            configuration on the Transport instance.
+	 * @return {@code this}
+	 */
+	public FetchCommand setTransportConfigCallback(
+			TransportConfigCallback transportConfigCallback) {
+		checkCallable();
+		this.transportConfigCallback = transportConfigCallback;
+		return this;
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/api/PullCommand.java

@@ -88,6 +88,8 @@ public class PullCommand extends GitCommand<PullResult> {
 
 	private CredentialsProvider credentialsProvider;
 
+	private TransportConfigCallback transportConfigCallback;
+
 	/**
 	 * @param repo
 	 */
@@ -127,6 +129,21 @@ public class PullCommand extends GitCommand<PullResult> {
 		return this;
 	}
 
+	/**
+	 * @param transportConfigCallback
+	 *            if set, the callback will be invoked after the Transport has
+	 *            created, but before the Transport is used. The callback can
+	 *            use this opportunity to set additional type-specific
+	 *            configuration on the Transport instance.
+	 * @return {@code this}
+	 */
+	public PullCommand setTransportConfigCallback(
+			TransportConfigCallback transportConfigCallback) {
+		checkCallable();
+		this.transportConfigCallback = transportConfigCallback;
+		return this;
+	}
+
 	/**
 	 * Executes the {@code Pull} command with all the options and parameters
 	 * collected by the setter methods (e.g.
@@ -214,6 +231,7 @@ public class PullCommand extends GitCommand<PullResult> {
 			fetch.setProgressMonitor(monitor);
 			fetch.setTimeout(this.timeout);
 			fetch.setCredentialsProvider(credentialsProvider);
+			fetch.setTransportConfigCallback(transportConfigCallback);
 
 			fetchRes = fetch.call();
 		} else {

org.eclipse.jgit/src/org/eclipse/jgit/api/PushCommand.java

@@ -95,6 +95,8 @@ public class PushCommand extends GitCommand<Iterable<PushResult>> {
 
 	private CredentialsProvider credentialsProvider;
 
+	private TransportConfigCallback transportConfigCallback;
+
 	/**
 	 * @param repo
 	 */
@@ -151,6 +153,8 @@ public class PushCommand extends GitCommand<Iterable<PushResult>> {
 				transport.setDryRun(dryRun);
 				if (credentialsProvider != null)
 					transport.setCredentialsProvider(credentialsProvider);
+				if (transportConfigCallback != null)
+					transportConfigCallback.configure(transport);
 
 				final Collection<RemoteRefUpdate> toPush = transport
 						.findRemoteRefUpdatesFor(refSpecs);
@@ -431,4 +435,19 @@ public class PushCommand extends GitCommand<Iterable<PushResult>> {
 		this.credentialsProvider = credentialsProvider;
 		return this;
 	}
+
+	/**
+	 * @param transportConfigCallback
+	 *            if set, the callback will be invoked after the Transport has
+	 *            created, but before the Transport is used. The callback can
+	 *            use this opportunity to set additional type-specific
+	 *            configuration on the Transport instance.
+	 * @return {@code this}
+	 */
+	public PushCommand setTransportConfigCallback(
+			TransportConfigCallback transportConfigCallback) {
+		checkCallable();
+		this.transportConfigCallback = transportConfigCallback;
+		return this;
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/api/TransportConfigCallback.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2011, Roberto Tyley <roberto.tyley@gmail.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.api;
+
+import org.eclipse.jgit.transport.Transport;
+
+/**
+ * Receives a callback allowing type-specific configuration to be set
+ * on the Transport instance after it's been created.
+ * <p>
+ * This allows consumers of the JGit command API to perform custom
+ * configuration that would be difficult anticipate and expose on the
+ * API command builders.
+ * <p>
+ * For instance, if a client needs to replace the SshSessionFactorys
+ * on any SSHTransport used (eg to control available SSH identities),
+ * they can set the TransportConfigCallback on the JGit API command -
+ * once the transport has been created by the command, the callback
+ * will be invoked and passed the transport instance, which the
+ * client can then inspect and configure as necessary.
+ */
+public interface TransportConfigCallback {
+
+	/**
+	 * Add any additional transport-specific configuration required.
+	 * @param transport
+	 */
+	public void configure(Transport transport);
+}