Add engine option to graph generation (#476)

tools/turbinia_job_graph.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python -v
+#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 # Copyright 2018 Google Inc.
 #
@@ -54,16 +54,36 @@ def create_graph():
       description='Create Turbinia evidence graph.')
   parser.add_argument(
       '-f', '--format', default='png',
-      help='The format of the output file you wish to generate.  Supported '
-      'types are here: http://www.graphviz.org/doc/info/output.html')
+      help='The format of the output file you wish to generate.  Specify '
+      '"list" to list out the available output types.  More info is here: '
+      'http://www.graphviz.org/doc/info/output.html')
+  parser.add_argument(
+      '-e', '--engine', default='dot',
+      help='The graphviz engine used to generate the graph layout.  Specify '
+      '"list" to list out the available engines.')
   parser.add_argument('filename', type=unicode, help='where to save the file')
   args = parser.parse_args()
 
+  if args.format == 'list':
+    formats = ' '.join(graphviz.FORMATS)
+    print('Available format types: {0:s}'.format(formats))
+    sys.exit(0)
+
   if args.format not in graphviz.FORMATS:
     print('Format type {0:s} is not supported'.format(args.format))
     sys.exit(1)
 
+  if args.engine == 'list':
+    engines = ' '.join(graphviz.ENGINES)
+    print('Available graph layout engines: {0:s}'.format(engines))
+    sys.exit(0)
+
+  if args.engine not in graphviz.ENGINES:
+    print('Layout engine type {0:s} is not supported'.format(args.engine))
+    sys.exit(1)
+
   graph = create_graph()
+  graph.engine = args.engine
   output_file = args.filename.replace('.png', '')
 
   try: