patman: Add a -D option to enable debugging

Most users don't want to see traceback errors. Add an option to enable
them for debugging. Disable them by default.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/main.py b/tools/patman/main.py
index 77f187e..b960008 100755
--- a/tools/patman/main.py
+++ b/tools/patman/main.py
@@ -10,6 +10,7 @@
 import os
 import re
 import sys
+import traceback
 import unittest
 
 if __name__ == "__main__":
@@ -34,6 +35,8 @@
         default=-1, help='Automatically create patches from top n commits')
     parser.add_argument('-e', '--end', type=int, default=0,
         help='Commits to skip at end of patch list')
+    parser.add_argument('-D', '--debug', action='store_true',
+        help='Enabling debugging (provides a full traceback on error)')
     parser.add_argument('-s', '--start', dest='start', type=int,
         default=0, help='Commit to start creating patches from (0 = HEAD)')
 
@@ -98,6 +101,9 @@
 if __name__ != "__main__":
     pass
 
+if not args.debug:
+    sys.tracebacklimit = 0
+
 # Run our meagre tests
 if args.cmd == 'test':
     import doctest