read command parameters from config sections (#240)

* read command parameters from config sections

* README: update config file documentation

* README: config example type INI, add comma

* README: clearer and better spelled wording

* README: fix 'delineated' typo

README.md

@@ -157,42 +157,45 @@ The simplest way to get started making accurate rips is:
 
 ## Configuration file documentation
 
-The configuration file is stored according to the [XDG Base Directory Specification](
-http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html)
-when possible.
+The configuration file is stored in  
+`$XDG_CONFIG_HOME/whipper/whipper.conf`, or  
+`$HOME/.config/whipper/whipper.conf` if `$XDG_CONFIG_HOME` is undefined.
 
-It lives in `$XDG_CONFIG_HOME/whipper/whipper.conf` (or `$HOME/.config/whipper/whipper.conf`).
+See [XDG Base Directory
+Specification](http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html)
+and [ConfigParser](https://docs.python.org/2/library/configparser.html).
 
-The configuration file follows python's [ConfigParser](https://docs.python.org/2/library/configparser.html) syntax.
+The configuration file consists of newline-delineated `[sections]`
+containing `key = value` pairs. The sections `[main]` and
+`[musicbrainz]` are special config sections for options not accessible
+from the command line interface.  Sections beginning with `drive` are
+written by whipper; certain values should not be edited.
 
-The possible sections are:
+Example configuration demonstrating all `[main]` and `[musicbrainz]`
+options:
 
-- Main section: `[main]`
-  - `path_filter_fat`: whether to filter path components for FAT file systems
-  - `path_filter_special`: whether to filter path components for special characters
-  
-- MusicBrainz section: `[musicbrainz]`
-  - `server`: the MusicBrainz server to connect to, in `host:[port]` format. Defaults to `musicbrainz.org`.
+```INI
+[main]
+path_filter_fat = True		; replace FAT file system unsafe characters in filenames with _
+path_filter_special = False	; replace special characters in filenames with _
 
-- Drive section: `[drive:IDENTIFIER]`, one for each configured drive. All these values are probed by whipper and should not be edited by hand.
-  - `defeats_cache`: whether this drive can defeat the audio cache
-  - `read_offset`: the read offset of the drive
+[musicbrainz]
+server = musicbrainz.org:80	; use musicbrainz server at host[:port]
 
-- Rip command section: `[rip.COMMAND.SUBCOMMAND]`. Can be used to change the command options default values.
-  **Please note that this feature is currently broken (being this way since [PR #122](https://github.com/JoeLametta/whipper/pull/92) / whipper [v0.4.1](https://github.com/JoeLametta/whipper/releases/tag/v0.4.1)).**
+[drive:HL-20]
+defeats_cache = True		; whether the drive is capable of defeating the audio cache
+read_offset = 6			; drive read offset in positive/negative frames (no leading +)
+# do not edit the values 'vendor', 'model', and 'release'; they are used by whipper to match the drive
 
-Example section to configure `whipper cd rip` defaults:
-
-```Python
-[rip.cd.rip]
+# command line defaults for `whipper cd rip`
+[whipper.cd.rip]
 unknown = True
 output_directory = ~/My Music
-track_template = new/%%A/%%y - %%d/%%t - %%n
+track_template = new/%%A/%%y - %%d/%%t - %%n	; note: the format char '%' must be represented '%%'
 disc_template = %(track_template)s
+# ...
 ```
 
-Note: to get a literal `%` character it must be doubled.
-
 ## Backward incompatible changes
 
 - Rely on `cd-paranoia` (`libcdio-cdparanoia`) instead of `cdparanoia` (Xiph): changed dependency ([PR #213](https://github.com/JoeLametta/whipper/pull/213) / whipper [v0.6.0](https://github.com/JoeLametta/whipper/releases/tag/v0.6.0))

whipper/command/basecommand.py

@@ -5,7 +5,7 @@ import argparse
 import os
 import sys
 
-from whipper.common import drive
+from whipper.common import config, drive
 
 import logging
 logger = logging.getLogger(__name__)
@@ -27,11 +27,13 @@ logger = logging.getLogger(__name__)
 
 class BaseCommand():
     """
-    A base command class for whipper commands.
+    Register and handle whipper command arguments with ArgumentParser.
 
-    Creates an argparse.ArgumentParser.
-    Override add_arguments() and handle_arguments() to register
-    and process arguments before & after argparse.parse_args().
+    Register arguments by overriding `add_arguments()` and modifying
+    `self.parser`. Option defaults are read from the dot-separated
+    `prog_name` section of the config file (e.g., 'whipper cd rip'
+    options are read from '[whipper.cd.rip]'). Runs
+    `argparse.parse_args()` then calls `handle_arguments()`.
 
     Provides self.epilog() formatting command for argparse.
 
@@ -57,6 +59,19 @@ class BaseCommand():
         self.init_parser()
         self.add_arguments()
 
+        config_section = prog_name.replace(' ', '.')
+        defaults = {}
+        for action in self.parser._actions:
+            val = None
+            if isinstance(action, argparse._StoreAction):
+                val = config.Config().get(config_section, action.dest)
+            elif isinstance(action, (argparse._StoreTrueAction,
+                                     argparse._StoreFalseAction)):
+                val = config.Config().getboolean(config_section, action.dest)
+            if val is not None:
+                defaults[action.dest] = val
+        self.parser.set_defaults(**defaults)
+
         if hasattr(self, 'subcommands'):
             self.parser.add_argument('remainder',
                                      nargs=argparse.REMAINDER,