Add support for a "help" action that prints the driver module's docst…

…ring.

This allows the drivers to provide information on what they support
directly, rather than relying on the README file. It also allows to provide
further information for the quirkier devices.

This is again trying to resolve Issue #9.

glucometer.py

@@ -9,6 +9,7 @@
 
 import argparse
 import importlib
+import inspect
 import logging
 import sys
 
@@ -34,6 +35,9 @@ def main():
     help=('Python logging level. See the levels at '
           'https://docs.python.org/3/library/logging.html#logging-levels'))
 
+  subparsers.add_parser(
+    'help', help=('Display a description of the driver, including supported '
+                  'features and known quirks.'))
   subparsers.add_parser(
     'info', help='Display information about the meter.')
   subparsers.add_parser(
@@ -67,6 +71,12 @@ def main():
       args.driver)
     return 1
 
+  # This check needs to happen before we try to initialize the device, as the
+  # help action does not require a --device at all.
+  if args.action == 'help':
+    print(inspect.getdoc(driver))
+    return 0
+
   device = driver.Device(args.device)
 
   device.connect()

glucometerutils/drivers/sdcodefree.py

@@ -1,5 +1,18 @@
 # -*- coding: utf-8 -*-
-"""Driver for SD CodeFree devices by SD Biosensor"""
+"""Driver for SD CodeFree devices by SD Biosensor.
+
+For SD Biosensor glucometers using the serial interface.
+
+Supported features:
+    - get readings, including pre-/post-meal notes;
+    - set date and time.
+
+Expected device path: /dev/ttyUSB0 or similar serial port device.
+
+IMPORTANT NOTE: the glucometer can be connected before starting the program, but
+it has to be turned on when the program asks you to.
+"""
+
 
 __author__ = 'Diego Elio Pettenò'
 __email__ = 'flameeyes@flameeyes.eu'