implemented set_field cli parsing

beets/config_default.yaml

@@ -25,7 +25,8 @@ import:
     pretend: false
     search_ids: []
     duplicate_action: ask
-    bell: no  
+    bell: no
+    set_fields: {}
 
 clutter: ["Thumbs.DB", ".DS_Store"]
 ignore: [".*", "*~", "System Volume Information", "lost+found"]

beets/ui/__init__.py

@@ -1060,6 +1060,24 @@ class SubcommandsOptionParser(CommonOptionsParser):
         suboptions, subargs = subcommand.parse_args(args)
         return subcommand, suboptions, subargs
 
+    @staticmethod
+    def _store_dict(option, opt_str, value, parser):
+        """Custom action callback to parse options which have ``key=value``
+        pairs as values. All such pairs passed for this option are
+        aggregated into a dictionary.
+        """
+        dest = option.dest
+        option_values = getattr(parser.values, dest, None)
+
+        if option_values is None:
+            # This is the first supplied ``key=value`` pair of option.
+            # Initialize empty dictionary and get a reference to it.
+            setattr(parser.values, dest, dict())
+            option_values = getattr(parser.values, dest)
+
+        key, value = value.split('=')
+        option_values[key] = value
+
 
 optparse.Option.ALWAYS_TYPED_ACTIONS += ('callback',)
 

beets/ui/commands.py

@@ -40,6 +40,7 @@ from beets import config
 from beets import logging
 from beets.util.confit import _package_path
 import six
+from . import SubcommandsOptionParser
 
 VARIOUS_ARTISTS = u'Various Artists'
 PromptChoice = namedtuple('PromptChoice', ['short', 'long', 'callback'])
@@ -1017,6 +1018,11 @@ import_cmd.parser.add_option(
     metavar='ID',
     help=u'restrict matching to a specific metadata backend ID'
 )
+import_cmd.parser.add_option(
+    u'--set-field', dest='set_fields', action='callback', callback=SubcommandsOptionParser._store_dict,
+    metavar='FIELD=VALUE',
+    help=u'set the given fields to the supplied values after importing'
+)
 import_cmd.func = import_func
 default_commands.append(import_cmd)