Merging input files

[ The documentation for this feature is incomplete. Please bear with us. ]

For a detailed description of the problem, see the description of issue #6071. Secondary file reading is now possible using the following syntax in your FHiCL configuration:

source: {

  module_type: RootInput

  fileNames: [ "primary.root"]

  secondaryFileNames: [
      a: "primary.root" 
      b: [ "secondary_1.root", "secondary_2.root", ... ]


where the secondary files for a given primary file are specified by the secondaryFileNames sequence, where each entry is a table that maps the primary file (signified by 'a') to a list of secondary files from where data products can be retrieved (signified by the sequence 'b').