pgm: Handle IOException in MergeBase command

This avoids we show a stacktrace on the console by default when this
type of exception is thrown during the run method is executed.

Change-Id: I5f198f71adfbb43ec1af26285658a5d5bdfa1904
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

 
 package org.eclipse.jgit.pgm;
 
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 
 
 	/** {@inheritDoc} */
 	@Override
-	protected void run() throws Exception {
-		for (RevCommit c : commits)
-			argWalk.markStart(c);
-		argWalk.setRevFilter(RevFilter.MERGE_BASE);
-		int max = all ? Integer.MAX_VALUE : 1;
-		while (max-- > 0) {
-			final RevCommit b = argWalk.next();
-			if (b == null)
-				break;
-			outw.println(b.getId().name());
+	protected void run() {
+		try {
+			for (RevCommit c : commits)
+				argWalk.markStart(c);
+			argWalk.setRevFilter(RevFilter.MERGE_BASE);
+			int max = all ? Integer.MAX_VALUE : 1;
+			while (max-- > 0) {
+				final RevCommit b = argWalk.next();
+				if (b == null)
+					break;
+				outw.println(b.getId().name());
+			}
+		} catch (IOException e) {
+			throw die(e.getMessage(), e);
 		}
 	}
 }