Add "gmg raw_alembic" command.

This allows you to dispatch to the "alembic" command line tool properly,
but properly respecting MediaGoblin's own configuration.

mediagoblin/gmg_commands/__init__.py

@@ -76,6 +76,12 @@ SUBCOMMAND_MAP = {
         'setup': 'mediagoblin.gmg_commands.batchaddmedia:parser_setup',
         'func': 'mediagoblin.gmg_commands.batchaddmedia:batchaddmedia',
         'help': 'Add many media entries at once'},
+    'alembic': {
+        'setup': 'mediagoblin.gmg_commands.alembic:parser_setup',
+        'func': 'mediagoblin.gmg_commands.alembic:raw_alembic_cli',
+        'help': (
+            'Run raw alembic commands with our local database.  '
+            '(Unless you know what you\'re doing, use dbupdate instead!)')},
     # 'theme': {
     #     'setup': 'mediagoblin.gmg_commands.theme:theme_parser_setup',
     #     'func': 'mediagoblin.gmg_commands.theme:theme',

mediagoblin/gmg_commands/alembic.py

@@ -0,0 +1,54 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2011, 2012 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import argparse
+import os
+
+from alembic import config
+from sqlalchemy.orm import sessionmaker
+
+from mediagoblin.db.open import setup_connection_and_db_from_config
+from mediagoblin.init import setup_global_and_app_config
+
+
+class FudgedCommandLine(config.CommandLine):
+    def main(self, args, db):
+        options = self.parser.parse_args(args.args_for_alembic)
+        if not hasattr(options, "cmd"):
+            print(
+                "* Only use this command if you know what you are doing! *\n"
+                "If not, use the 'gmg dbupdate' command instead.\n\n"
+                "Alembic help:\n")
+            self.parser.print_help()
+            return
+        else:
+            Session = sessionmaker(bind=db.engine)
+
+            root_dir = os.path.abspath(os.path.dirname(os.path.dirname(
+                os.path.dirname(__file__))))
+            alembic_cfg_path = os.path.join(root_dir, 'alembic.ini')
+            cfg = config.Config(alembic_cfg_path,
+                                cmd_opts=options)
+            cfg.attributes["session"] = Session()
+            self.run_cmd(cfg, options)
+        
+def parser_setup(subparser):
+    subparser.add_argument("args_for_alembic", nargs=argparse.REMAINDER)
+
+def raw_alembic_cli(args):
+    global_config, app_config = setup_global_and_app_config(args.conf_file)
+    db = setup_connection_and_db_from_config(app_config, migrations=False)
+    FudgedCommandLine().main(args, db)