lacre.admin: Add -r / --reload option to import command

With -r option, import command will first remove all identities and then load
them again from pubring.kbx.

lacre/admin.py

@@ -70,6 +70,9 @@ def sub_import(args):
     conn = repo.connect(conf.get_item('database', 'url'))
     identities = repo.IdentityRepository(conn)
 
+    if args.reload:
+        identities.delete_all()
+
     total = 0
     for (fingerprint, email) in public.items():
         LOG.debug('Importing %s - %s', email, fingerprint)
@@ -97,7 +100,10 @@ def main():
     cmd_import = sub_commands.add_parser('import',
         help='Load identities from GnuPG directory to Lacre database'
         )
-    cmd_import.add_argument('-d', '--homedir', help='specify GnuPG directory (default: use configured dir.)')
+    cmd_import.add_argument('-d', '--homedir', default=False,
+                            help='specify GnuPG directory (default: use configured dir.)')
+    cmd_import.add_argument('-r', '--reload',
+                            help='delete all keys from database before importing')
     cmd_import.set_defaults(operation=sub_import)
 
     cmd_queue = sub_commands.add_parser('queue',

lacre/repositories.py

@@ -71,6 +71,12 @@ class IdentityRepository(KeyRing):
 
         self._conn.execute(delq)
 
+    def delete_all(self):
+        LOG.warn('Deleting all identities from the database')
+
+        delq = delete(self._identities)
+        self._conn.execute(delq)
+
     def freeze_identities(self) -> KeyCache:
         """Return a static, async-safe copy of the identity map."""
         self._ensure_connected()