introduce custom object for cmdline arguments

Allows to define special functions over the arguments.

Also splits CLI tests in two files as they have become too many.

nominatim/clicmd/args.py

@@ -0,0 +1,22 @@
+"""
+Provides custom functions over command-line arguments.
+"""
+
+
+class NominatimArgs:
+    """ Customized namespace class for the nominatim command line tool
+        to receive the command-line arguments.
+    """
+
+    def osm2pgsql_options(self, default_cache, default_threads):
+        """ Return the standard osm2pgsql options that can be derived
+            from the command line arguments. The resulting dict can be
+            further customized and then used in `run_osm2pgsql()`.
+        """
+        return dict(osm2pgsql=self.config.OSM2PGSQL_BINARY or self.osm2pgsql_path,
+                    osm2pgsql_cache=self.osm2pgsql_cache or default_cache,
+                    osm2pgsql_style=self.config.get_import_style_file(),
+                    threads=self.threads or default_threads,
+                    dsn=self.config.get_libpq_dsn(),
+                    flatnode_file=self.config.FLATNODE_FILE)
+