plainbox puts too many jobs in a session, causing spurious resume failures

[Jonathan Cave]

Version: 0.14+bzr3326+pkg15~ubuntu14.10.1

On trying to resume a session (imported from another user), I was presented with following error:

$ plainbox run -i 2014.com.canonical.foobar::.* -f html -o report.html
=========================[ Resume Incomplete Session ]==========================
There is 1 incomplete session that might be resumed
Do you want to resume session 'pbox-my25w8u6'?
  r => resume this session
  n => next session
  c => create new session
[rnc]: r
Definition of job '2013.com.canonical.certification::bluetooth/audio' has changed
This session cannot be resumed
Pick an action
  i => ignore this problem
  e => erase this session
[ie]:

[Zygmunt Krynicki (zyga)]

This error happens when the user has two providers, say A and B. The user starts a test session with a few jobs from the B provider selected. Meanwhile the session is stopped and the A provider gets updated. After that the user won't be able to resume the session even though that none of the jobs in B were changed.

[Daniel Manrique (roadmr)]

Here's a reproduction case:

- From source, mk-venv and activate the virtual environment
- run this:
plainbox run -i 2013.com.canonical.certification::memory/info
- As soon as you see the tiny scissors (... 8< ---), hit ctrl-c to interrupt the session
- Edit providers/plainbox-provider-resource/generic/jobs/resource.txt and modify the description for any of the jobs in there (cdimage is good as it's not really used in the run).
- Rerun the plainbox command as seen above
- Select resuming the session

it will complain about a modified job.

With the proposed patch in place, this sequence doesn't give problems.