[ANN] Announcing new extension for alternative subrepo functionality.

[ben_smith at selinc.com]

> What is the minimum mercurial version this extension works with?
Guestrepo supports python >= 2.4 and Mercurial >= 1.9

Paul made a small error:
The line:
    grfreeze > .hggrfrozen
should be changed to:
   hg grstate > .hggrfrozen

The grstate command outputs the same guest repos' states to standard out.

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Ben Smith