Added request header downgrade for COPY command to work on https setup. Fixes #4307

docs/admin/vcs-server.rst

@@ -327,6 +327,8 @@ Once installed you need to enable ``dav_svn``:
 .. code-block:: bash
 
     $ sudo a2enmod dav_svn
+    $ sudo a2enmod headers
+
 
 Configuring Apache Setup
 ========================

rhodecode/svn_support/templates/mod-dav-svn.conf.mako

@@ -36,6 +36,9 @@
 # After changing this a stop and start of Apache is required (using restart
 # doesn't work).
 
+# fix https -> http downgrade with DAV. It requires an header downgrade for
+# https -> http reverse proxy to work properly
+RequestHeader edit Destination ^https: http: early
 
 <Location "${location_root|n}">
     # The mod_dav_svn module takes the username from the apache request object.