checker: print what linters are to be installed and the results of that

viewer: show commit branch as a separate list item

checker: emit commit branch on its own line

checker: split a long line

checker: start setting useful environment variables

incoming: sometimes checker output is totally useless

checker: prevalidate config (basic checks)

viewer: create collapsers wholly on client-side

viewer: don't collapse checks block by default, everything else is fine

checker: a config without linters is useless, but valid