That version of bash we’ve been using on MacOS since forever hasn’t been updated since forever (for GPL licensing reasons). With Catalina, Apple finally got with the program and pushed bash into the background in favor of zsh. Nothing earth-shattering there – zsh has been available forever, but now it’s the default, and the Terminal will bug you on every launch if you don’t follow its instructions to migrate.
Once you do move over, run don’t walk to Oh My Zsh for a wonderful rabbit hole of themes, plugins, and configuration options to make zsh sing for you. By default, it knows how to detect whether the current directory contains a git checkout, and will show the active branch in the prompt, which is worth the price of admission alone.