We may need to provide a help page that describes exactly how the so called "CommonsHelper2" configuration pages work, down to the exact syntax. At the moment, all we have is:

• Some lists of the feature set, but not how to pull them off.
  • https://meta.wikimedia.org/wiki/WMDE_Technical_Wishes/Move_files_to_Commons/Template_matching
  • https://gerrit.wikimedia.org/r/443102
• Thanks to @Magnus' the format is almost entirely self-documented, which allows the users to copy-paste e.g. https://www.mediawiki.org/wiki/Extension:FileImporter/Data/en.wikipedia and adapt it to any other wiki.

At least these error message should bring up a link to that help page:

• fileimporter-commonshelper-parsing-failed
• fileimporter-commonshelper-missing-config, introduced via https://gerrit.wikimedia.org/r/475091.