Make bzr revno --tree available without net access on lightweight checkouts

[Christian Faulhammer]

In Gentoo we use lightweight checkouts for live ebuilds (aka build from the repository head and have it installed under the control of our package manager). For an additional tool we check for the state of the last checkout and want to access the revision number, which is not a problem when having internet access, but we want to be able to do that without any access there. For a non-lightweight checkout the revision is stored in .bzr/branch/last-revision which is a tiny file, one line of text only, maybe this could be provided for the lightweight version, too.
Thanks in advance for the work.

[John A Meinel (jameinel)]

It isn't really trivial, since it would require a disk format change. But it is something we could consider.

Note that at present, doing *any* operation on a lightweight checkout will always connect to its associated branch (even if it could be answered from the checkout itself). (I think there is an open wishlist bug to avoid that as well)