Use ruby's oneshot_coverage to detect code executed in rails app.
勉強したこと
annotations/cheat sheets
gzip compression output - it is just a mirror with applied patches
Lint your Ruby code in parallel to your builds
Rails upgrade's best friend
A gem to automate using Croppie with Rails
Manifest for rubyci, gem-codesearch and etc
Tool collection to write and layout programmer's manuals.