Update configs if the config is in the branch and changes

[Elliot Murphy]

> Ubunet has two sourcedeps under very active development:
> > ubuntuone-client and ubuntuone-storage-protocol. Sometimes, we need to
> > make changes in both of those sourcedeps, and then update some tests in
> > the main ubunet branch and land the whole mess all at once. Currently
> > this is pretty fragile, and results in PQM being broken for some window
> > of time.
> >
> > I've been working on fixing this, as you know in rev 161 of
> > lp:config-manager you merged support for telling config-manager the
> > revision number of a branch that should be pulled into sourcedeps.
> >
> > The next step is to version control the config-manager.txt config file
> > that is used to load all the sourcedeps, and to make pqm use the version
> > of sourcedeps that are specified in the branch under test. This gives us
> > a bit of a chicken-and-egg problem, since before running tests, pqm uses
> > config-manager to get the main trunk branch (and currently all of the
> > sourcedeps) to merge into.

I think the most elegant thing would be to have PQM check out the branch
and then build the contained config; with the config not being self
referential.

This needs a [small] tweak to PQM.
Currently the logic is
if build-a-config:
  read the config
  build it
  find the branch being targeted in the config

I think
if build-a-config:
  try:
     read the config
  except (config not found, branch not in config):
     branch the target
     merge the source
     read the config
     build it ignoring the branch being targeted

would be all thats needed. That would preserve a branch at ., which is
what cm.py uses to update the root (which can contain the config). cm.py
may need a tweak to know to process the config twice if the config
changes when updating a containing branch.

So - two small bugs, I think.

-Rob

[Tim Cole (tcole)]

I've done a branch (versioned-sourcedeps) which splits out sourcedeps branch and revision information into a distinct configuration file.

Now to wire that file up with pqm/config-manager somehow, I guess.

[Tim Cole (tcole)]

Updating to critical because the version trainwrecks really are stopping work.

[Tim Cole (tcole)]

Next step is to get the new version of PQM available for ubunet PQM. This is RT 35521.

[Joshua Hoover (joshuahoover)]

Discussed during bug triage call and determined this is not critical and not necessarily needed for Karmic release.

[Tim Cole (tcole)]

It looks like the remaining work to be done is in config-manager -- with bzr, update (versus build) is apparently only capable of fast-forwarding the tree. We unfortunately need more than that.