This is actually not new, the command is there for a long time, but it is one of those things that help and you keep forgetting about.
It works by searching your code for comments with specific keywords, the default is searching for FIXME, OPTIMIZE and TODO.
You can add more tags either by using the “–annotations” parameter or by registering the tags in your rails config
config.annotations.register_tags("DEPRECATEME", "TESTME")
The output is pretty simple and yet helpful, for example this is the output of one of my projects:
$rails notes app/controllers/some_controller_with_domains.rb: * [ 67] [FIXME] need to check allowed domains * [ 86] [FIXME] need to check allowed domains app/controllers/search_controller.rb: * [ 71] [FIXME] ugly hack for exact match * [190] [FIXME] ugly hack for exact match app/webpacker/javascript/core/components/SomeJavascriptFile.js: * [ 33] [TODO] Remove from collection if status no longer matches search * [167] [TODO] Not implemented app/webpacker/javascript/core/components/SomeOtherJavascriptFIle.js: * [ 38] [FIXME] not actually properly memoized app/webpacker/javascript/core/components/JavascriptWithWeirdness.js: * [107] [FIXME] Weirdness on first update