[sshd agent] Introduce ConnectorDescriptor

Once a factory supports different SSH agents on the same platform,
which is planned for Windows once we use Apache MINA sshd 2.8.0,
client code may need to have a way to specify which SSH agent shall
be used when the SSH config doesn't define anything.

Add a mechanism by which a ConnectorFactory can tell what Connectors
it may provide. Client code can use this to set the identityAgent
parameter of ConnectorFactory.create() to the wanted default if it
would be null otherwise.

A ConnectorDescriptor is a pair of strings: an internal name, and a
display name. The latter is included because client code might want to
communicate agent names to the user, be it in error messages or in some
chooser dialog where a user could define which of several alternative
SSH agents should be used as default. The internal name is intended to
be used in the IdentityAgent directive in ~/.ssh/config.

Also make the ConnectorFactory discovered via the ServiceLoader
accessible and overrideable. Provide static get/setDefault() methods,
similar to the SshSessionFactory itself.

Change-Id: Ie3d077395d32dfddc72bc8627e92b23636938182
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

4 files changed, 60 insertions, 0 deletions

diff --git a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Factory.java b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Factory.java
index 1cbf0e41b6..d7409b0c3c 100644
--- a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Factory.java
+++ b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Factory.java
@@ -11,6 +11,8 @@ package org.eclipse.jgit.internal.transport.sshd.agent.connector;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.Collection;
+import java.util.Collections;
 
 import org.eclipse.jgit.transport.sshd.agent.Connector;
 import org.eclipse.jgit.transport.sshd.agent.ConnectorFactory;
@@ -41,4 +43,26 @@ public class Factory implements ConnectorFactory {
 	public String getName() {
 		return NAME;
 	}
+
+	/**
+	 * {@inheritDoc}
+	 * <p>
+	 * This factory returns on Windows a
+	 * {@link org.eclipse.jgit.transport.sshd.agent.ConnectorFactory.ConnectorDescriptor
+	 * ConnectorDescriptor} for the internal name "pageant"; on Unix one for
+	 * "SSH_AUTH_SOCK".
+	 * </p>
+	 */
+	@Override
+	public Collection<ConnectorDescriptor> getSupportedConnectors() {
+		return Collections.singleton(getDefaultConnector());
+	}
+
+	@Override
+	public ConnectorDescriptor getDefaultConnector() {
+		if (SystemReader.getInstance().isWindows()) {
+			return PageantConnector.DESCRIPTOR;
+		}
+		return UnixDomainSocketConnector.DESCRIPTOR;
+	}
 }
diff --git a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/PageantConnector.java b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/PageantConnector.java
index 59fe2fc246..b0e3bce724 100644
--- a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/PageantConnector.java
+++ b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/PageantConnector.java
@@ -12,12 +12,29 @@ package org.eclipse.jgit.internal.transport.sshd.agent.connector;
 import java.io.IOException;
 
 import org.eclipse.jgit.transport.sshd.agent.AbstractConnector;
+import org.eclipse.jgit.transport.sshd.agent.ConnectorFactory.ConnectorDescriptor;
 
 /**
  * A connector using Pageant's shared memory IPC mechanism.
  */
 public class PageantConnector extends AbstractConnector {
 
+	/**
+	 * {@link ConnectorDescriptor} for the {@link PageantConnector}.
+	 */
+	public static final ConnectorDescriptor DESCRIPTOR = new ConnectorDescriptor() {
+
+		@Override
+		public String getIdentityAgent() {
+			return "pageant"; //$NON-NLS-1$
+		}
+
+		@Override
+		public String getDisplayName() {
+			return Texts.get().pageant;
+		}
+	};
+
 	private final PageantLibrary lib;
 
 	/**
diff --git a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Texts.java b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Texts.java
index 6b66261546..fb45b30dd2 100644
--- a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Texts.java
+++ b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/Texts.java
@@ -42,5 +42,7 @@ public final class Texts extends TranslationBundle {
 	/***/ public String msgSendFailed2;
 	/***/ public String msgSharedMemoryFailed;
 	/***/ public String msgShortRead;
+	/***/ public String pageant;
+	/***/ public String unixDefaultAgent;
 
 }
diff --git a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/UnixDomainSocketConnector.java b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/UnixDomainSocketConnector.java
index 4c698d974a..3b75f3a7da 100644
--- a/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/UnixDomainSocketConnector.java
+++ b/org.eclipse.jgit.ssh.apache.agent/src/org/eclipse/jgit/internal/transport/sshd/agent/connector/UnixDomainSocketConnector.java
@@ -24,6 +24,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.apache.sshd.common.SshException;
 import org.eclipse.jgit.transport.sshd.agent.AbstractConnector;
+import org.eclipse.jgit.transport.sshd.agent.ConnectorFactory.ConnectorDescriptor;
 import org.eclipse.jgit.util.StringUtils;
 import org.eclipse.jgit.util.SystemReader;
 import org.slf4j.Logger;
@@ -38,6 +39,22 @@ import com.sun.jna.platform.unix.LibCAPI;
  */
 public class UnixDomainSocketConnector extends AbstractConnector {
 
+	/**
+	 * {@link ConnectorDescriptor} for the {@link UnixDomainSocketConnector}.
+	 */
+	public static final ConnectorDescriptor DESCRIPTOR = new ConnectorDescriptor() {
+
+		@Override
+		public String getIdentityAgent() {
+			return ENV_SSH_AUTH_SOCK;
+		}
+
+		@Override
+		public String getDisplayName() {
+			return Texts.get().unixDefaultAgent;
+		}
+	};
+
 	private static final Logger LOG = LoggerFactory
 			.getLogger(UnixDomainSocketConnector.class);