Add terminal size fit for side by side view

cdiff.py

@@ -503,6 +503,7 @@ class DiffMarker(object):
         except IndexError:
             max1 = max2 = 0
         num_width = max(len(str(max1)), len(str(max2)))
+        width -= num_width
 
         # Setup lineno and line format
         left_num_fmt = colorize('%%(left_num)%ds' % num_width, 'yellow')
@@ -664,6 +665,27 @@ def decode(line):
 
     return '*** cdiff: undecodable bytes ***\n'
 
+def terminal_size():
+    """
+    Returns terminal size.
+
+    Taken from this gist:
+    https://gist.github.com/marsam/7268750
+    """
+    width, height = None, None
+    if sys.platform == 'win32':
+        import win32utils
+        width, height = win32utils.get_console_size(defaultx=width, defaulty=height)
+    else:
+        try:
+            import struct, fcntl, termios
+            s = struct.pack('HHHH', 0, 0, 0, 0)
+            x = fcntl.ioctl(1, termios.TIOCGWINSZ, s)
+            height, width = struct.unpack('HHHH', x)[0:2]
+        except (IOError, AttributeError):
+            pass
+    return width, height
+
 
 def main():
     signal.signal(signal.SIGPIPE, signal.SIG_DFL)
@@ -701,7 +723,8 @@ def main():
         help='enable side-by-side mode')
     parser.add_option(
         '-w', '--width', type='int', default=80, metavar='N',
-        help='set text width for side-by-side mode, default is 80')
+        help='set text width for side-by-side mode. If set to "0", cdiff ' \
+             'will attempt to fit the terminal width.')
     parser.add_option(
         '-l', '--log', action='store_true',
         help='show log with changes from revision control')
@@ -717,6 +740,15 @@ def main():
 
     opts, args = parser.parse_args()
 
+    if opts.width == 0 and opts.side_by_side:
+        # Autodetection of text width according to terminal size
+        try:
+            # width = half the terminal size minus the 3 minimum padding chars
+            opts.width = (terminal_size()[0] - 3) / 2
+        except Exception:
+            # If terminal detection failed, set back to default
+            opts.width = 80
+
     if opts.log:
         diff_hdl = revision_control_log(args)
         if not diff_hdl: