mq: copy pager attributes back to qrepo.ui If the legacy pager extension is enabled, a pager is started through repo.ui at dispatch._runcommand(). After that, mqcommand() creates a qrepo with a fresh repo.baseui, at which point pager information was lost and another pager would be spawned by the modern pager interface. This is a minimal workaround for the problem.

registrar: host "dynamicdefault" constant by configitem object This is the common pattern seen in the other registrar classes.

configitems: register 'ui.editor'