pgm: Handle exceptions in Diff 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: Iba0e4338381519dc55c2892d95181ddfb881adf2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

@@ -62,6 +62,7 @@ import org.eclipse.jgit.diff.DiffFormatter;
 import org.eclipse.jgit.diff.RawTextComparator;
 import org.eclipse.jgit.diff.RenameDetector;
 import org.eclipse.jgit.dircache.DirCacheIterator;
+import org.eclipse.jgit.errors.RevisionSyntaxException;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.Repository;
@@ -177,7 +178,7 @@ class Diff extends TextBuiltin {
 
 	/** {@inheritDoc} */
 	@Override
-	protected void run() throws Exception {
+	protected void run() {
 		diffFmt.setRepository(db);
 		try {
 			if (cached) {
@@ -217,6 +218,8 @@ class Diff extends TextBuiltin {
 				diffFmt.format(oldTree, newTree);
 				diffFmt.flush();
 			}
+		} catch (RevisionSyntaxException | IOException e) {
+			throw die(e.getMessage(), e);
 		} finally {
 			diffFmt.close();
 		}