I've build something similar [0] but lives in the terminal and is fully open source if anyone prefer terminal based app but still wants to work with .http/rest files.
I don’t personally use Postman, but at work we use .http files, which are easy to version and manage with Git. The downside is that you’re almost entirely tied to VS Code and the REST Client extension. I’m not a big fan of VS Code myself (I use Vim), so if anyone interested, I created resterm [0] - a terminal client that works with .http or .rest files and adds some extra "nice-to-have" features. I’m currently working on adding OpenAPI spec importing.