Bump version, changelog and upgrade.rst

UPGRADE.rst

@@ -1,3 +1,33 @@
+Upgrading to v0.5.0
+===================
+
+This release completely changes the database schema and so requires upgrading
+it before starting the new version of the homeserver.
+
+The script "database-prepare-for-0.5.0.sh" should be used to upgrade the
+database. This will save all user information, such as logins and profiles, 
+but will otherwise purge the database. This includes messages, which
+rooms the home server was a member of and room alias mappings.
+
+If you would like to keep your history, please take a copy of your database
+file and ask for help in #matrix:matrix.org. The upgrade process is,
+unfortunately, non trivial and requires human intervention to resolve any
+resutling conflicts during the upgrade process.
+
+Before running the command the homeserver should be first completely 
+shutdown. To run it, simply specify the location of the database, e.g.:
+
+  ./database-prepare-for-0.5.0.sh "homeserver.db"
+
+Once this has successfully completed it will be safe to restart the 
+homeserver. You may notice that the homeserver takes a few seconds longer to 
+restart than usual as it reinitializes the database.
+
+On startup of the new version, users can either rejoin remote rooms using room
+aliases or by being reinvited. Alternatively, if any other homeserver sends a
+message to a room that the homeserver was previously in the local HS will 
+automatically rejoin the room.
+
 Upgrading to v0.4.0
 ===================