Feature request: Mirror off-site repository, with periodic pull/update (BB-1962)

I work on the illumos.org project. We sometimes find it useful to point new developers to your site as a convenient way to get their own new clones of illumos gate via:
https://bitbucket.org/illumos/illumos-gate

Presently, the above repository is updated by a cron job that BDHA runs periodically on one of his own servers. After learning of that, it occurred to me that this would be a very handy feature for bitbucket to offer. Basically, "mirror" some off-site repository, with periodic "hg pull" from that off-site repository. One might also want some way to examine the status (output) of the most recent "hg pull", in case the upstream parent changes location or goes away, etc.

Thanks for the great service!