• intrigeri's avatar
    When testing ISO build reproducibility, use the same APT snapshots in both builds (refs: #15107). · 2da49e69
    intrigeri authored
    Problem:
    
     - Our branches based on devel use "latest" snapshots for every APT archive used
       at build time => their reproducibly_build_Tails_ISO_* job will fail if any of
       these APT snapshots is updated between the start of the original build job
       and the start of the reproducibly_build_Tails_ISO_* job.
    
     - Our branches based on stable are also affected, but to a lesser degree: they
       use the "latest" snapshot only for the debian-security archive.
    
     - Any branch can be affected when the build is triggered by a Git push at an
       unfortunate time. But for some branches, the automatic daily build is
       _always_ affected: daily Jenkins job runs are scheduled in a deterministic
       manner, with a schedule based on the name of the branch. So inevitably, the
       automatic daily rebuild of _some_ branches will always fail to build
       reproducibly, because the failure condition ("APT snapshots is updated
       between the start of the original build job and the start of the
       reproducibly_build_Tails_ISO_* job") will always be met. There's no such
       active branch at the moment but we've seen that happen in the past.
    
    To fix that, let's ensure we use the same APT snapshots during the second build
    as the ones the first build used. Here's how.
    
    With this commit, we save the serials an ISO build used as a build artifact that
    the downstream reproducibly_build_Tails_ISO_* CI job will copy and then load
    environment from (using the Jenkins EnvInject Plugin).
    
    Therefore, in a given reproducibly_build_Tails_ISO_* CI job run, the
    APT_SNAPSHOTS_SERIALS environment variable will tell what APT snapshots were
    used by its upstream build_Tails_ISO_* CI job run. And finally, thanks to
    commit:aafdf8da and follow-ups, that downstream
    reproducibly_build_Tails_ISO_* CI job run will reuse the same snapshots.
    2da49e69