If you're looking for something really lightweight, I built a Chrome extension called Test API that addresses some of your pain points - it's completely offline, no accounts needed, and everything stays local on your machine.
https://chromewebstore.google.com/detail/test-api/bkndipmbnodeicgpmldococoiolcoicg?hl=en

The main limitation right now is it doesn't have import/export for collections yet (I'm actively working on that feature), so it might not solve your immediate Git workflow needs. But for quick API testing without the Postman bloat and online requirements, it could be useful for development work.

It's designed to be minimal and fast - no complex UI, just straightforward request testing when you need it.