[feature] Time stamp to APT repo hash API and buildd argument

[Robert C Jennings]

Our livecd-rootfs code today takes a timestamp and provides a view of the apt repo for that point-in-time. The code for this lives in https://git.launchpad.net/livecd-rootfs/tree/magic-proxy. We would like to transition to asking LP for the hash and requesting a build from a hash instead of what we have. Obviously we're at some risk today with the timing issues in parallel builds by providing a timestamp for buildd rather than a hash and we'd like to get that sorted.

Our request is:
* LP API to translate timestamp to hash
* LP buildd argument to pass in an apt hash

We can transition livecd-rootfs quite easily once we have this.

[Dimitri John Ledkov (xnox)]

And I think we need it for a set of archives. Ie. timestamp translation to hashes of: release, updates, security, proposed, ppa(s). Because well, hashes are per-suite.

[Colin Watson (cjwatson)]

A while back I described the same feature in more detail in bug 1765933, and I've been attaching relevant merge proposals in progress to that bug, so marking this as a duplicate.