Fix #59 with env variable CDIFF_OPTIONS

README.rst

 
       Note:
         Option parser will stop on first unknown option and pass them down to
-        underneath revision control
+        underneath revision control. Environment variable CDIFF_OPTIONS may be
+        used to specify default options that will be placed at the beginning
+        of the argument list.
 
 Read diff from local modification in a *Git/Mercurial/Svn* workspace (output
 from e.g. ``git diff``, ``svn diff``):
     cdiff -ls -w90              # set text width 90 as well
     cdiff -ls file1 dir2        # see log with changes of given files/dirs only
 
+Environment variable ``CDIFF_OPTIONS`` may be used to specify default options
+that will be placed at the beginning of the argument list, for example:
+
+.. code-block:: bash
+
+    export CDIFF_OPTIONS='-s -w0'
+    cdiff foo                   # equivalent to "cdiff -s -w0 foo"
+
 If you feel more comfortable with a command such as ``git cdiff`` to trigger
 the cdiff command, you may symlink the executable to one named ``git-cdiff``
 as follows:

cdiff.py

     # Hack: use OptionGroup text for extra help message after option list
     option_group = OptionGroup(
         parser, "Note", ("Option parser will stop on first unknown option "
-                         "and pass them down to underneath revision control"))
+                         "and pass them down to underneath revision control. "
+                         "Environment variable CDIFF_OPTIONS may be used to "
+                         "specify default options that will be placed at the "
+                         "beginning of the argument list."))
     parser.add_option_group(option_group)
 
-    opts, args = parser.parse_args()
+    # Place possible options defined in CDIFF_OPTIONS at the beginning of argv
+    cdiff_opts = [x for x in os.getenv('CDIFF_OPTIONS', '').split(' ') if x]
+    opts, args = parser.parse_args(cdiff_opts + sys.argv[1:])
 
     if opts.log:
         diff_hdl = revision_control_log(args)