Change Flask.__init__ to accept two new keyword arguments, host_matching and static_host. (#1560)

This enables host_matching to be set properly by the time the constructor adds
the static route, and enables the static route to be properly associated with
the required host.

Previously, you could only enable host_matching once your app was already
instantiated (e.g. app.url_map.host_matching = True), but at that point
the constructor would have already added the static route without host matching
and an associated host, leaving the static route in a broken state.

Fixes #1559.

CHANGES

@@ -14,6 +14,11 @@ Major release, unreleased
 - Change default configuration `JSONIFY_PRETTYPRINT_REGULAR=False`. jsonify()
   method returns compressed response by default, and pretty response in
   debug mode.
+- Change Flask.__init__ to accept two new keyword arguments, ``host_matching``
+  and ``static_host``. This enables ``host_matching`` to be set properly by the
+  time the constructor adds the static route, and enables the static route to
+  be properly associated with the required host. (``#1559``)
+
 
 Version 0.12.1
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