[cli] Use chaining credentials provider to enable .netrc

If available use credentials in .netrc otherwise prompt the user
if jgit command line needs credentials for remote operations.

Change-Id: Iea1f595618edfb87a37137db08bac8ca2d500ebc
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.console/src/org/eclipse/jgit/console/ConsoleCredentialsProvider.java

 import java.io.Console;
 
 import org.eclipse.jgit.errors.UnsupportedCredentialItem;
+import org.eclipse.jgit.transport.ChainingCredentialsProvider;
 import org.eclipse.jgit.transport.CredentialItem;
 import org.eclipse.jgit.transport.CredentialsProvider;
+import org.eclipse.jgit.transport.NetRCCredentialsProvider;
 import org.eclipse.jgit.transport.URIish;
 
 /** Interacts with the user during authentication by using the text console. */
 		if (c.cons == null)
 			throw new NoClassDefFoundError(
 					ConsoleText.get().noSystemConsoleAvailable);
-		CredentialsProvider.setDefault(c);
+		CredentialsProvider cp = new ChainingCredentialsProvider(
+				new NetRCCredentialsProvider(), c);
+		CredentialsProvider.setDefault(cp);
 	}
 
 	private final Console cons = System.console();