BuildDiff: slight cleanup

Dependencies

• [2] YKMAJOVQ BuildDiff: document what the inputs mean
• [3] 4CBVJEIS BuildDiff: move cmdBuilds from Controller/JobsetEval
• [4] NYIIFA32 BuildDiff: split out from JobsetEval GET impl

Change contents

• edit in src/lib/Hydra/Helper/BuildDiff.pm at line 11
  [3.336]→[3.336:355](∅→∅)
  −

  − use Data::Dumper;
• edit in src/lib/Hydra/Helper/BuildDiff.pm at line 19
  [3.372]

  [3.372]
  + # $builds is the list of current builds

  + # $builds2 is the list of previous (to-be-compared-to) builds
• edit in src/lib/Hydra/Helper/BuildDiff.pm at line 22
  [3.405]→[2.0:103](∅→∅)
  − # $builds is the list of current builds, and $builds2 is the list of previous (compared-to) builds