allow to chose upgrade branch

profile.conf

@@ -217,6 +217,12 @@ MATRIX_DEFAULT_CHARSET=kana
 
 [updates]
 # Section used by updates.sh
+#
+# UPDT_DEFAULT_BRANCH — Git branch used for update checks and upgrades.
+#   Defaults to 'master' when unset. Changing this value will cause
+#   profile_upgrade to automatically switch the local checkout to the new
+#   branch on the next upgrade and display a warning.
+#UPDT_DEFAULT_BRANCH=master
 
 [general]
 # General section allow to set any variable that can be used by the user.