Provide a root cause for aborted commands

Change-Id: Iafaa03dbacbe7f1b2b074d3294db988b08fdb0d7
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

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

@@ -86,6 +86,21 @@ public class Die extends RuntimeException {
 	 * @since 3.4
 	 */
 	public Die(boolean aborted) {
+		this(aborted, null);
+	}
+
+	/**
+	 * Construct a new exception reflecting the fact that the command execution
+	 * has been aborted before running.
+	 *
+	 * @param aborted
+	 *            boolean indicating the fact the execution has been aborted
+	 * @param cause
+	 *            can be null
+	 * @since 4.2
+	 */
+	public Die(boolean aborted, final Throwable cause) {
+		super(cause != null ? cause.getMessage() : null, cause);
 		this.aborted = aborted;
 	}
 

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

@@ -217,7 +217,7 @@ public abstract class TextBuiltin {
 		} catch (CmdLineException err) {
 			if (!help) {
 				this.errw.println(MessageFormat.format(CLIText.get().fatalError, err.getMessage()));
-				throw die(true);
+				throw die(true, err);
 			}
 		}
 
@@ -324,6 +324,19 @@ public abstract class TextBuiltin {
 		return new Die(aborted);
 	}
 
+	/**
+	 * @param aborted
+	 *            boolean indicating that the execution has been aborted before
+	 *            running
+	 * @param cause
+	 *            why the command has failed.
+	 * @return a runtime exception the caller is expected to throw
+	 * @since 4.2
+	 */
+	protected static Die die(boolean aborted, final Throwable cause) {
+		return new Die(aborted, cause);
+	}
+
 	String abbreviateRef(String dst, boolean abbreviateRemote) {
 		if (dst.startsWith(R_HEADS))
 			dst = dst.substring(R_HEADS.length());