ok, figured it out. in case it helps anyone in the future, i found my answer in the happy git doc...once i did the below and restarted it works just fine again. heads up for any puzzled mac users
15.2 RStudio Git pane disappears on Mac OS
After a Mac OS upgrade, you might need to trigger the Xcode command line tools to prompt you for what it needs, i.e. to re-install or re-agree to the license agreement. We have seen this cause the RStudio Git pane to disappear on a system where it was previously working. Use commands like these below to tickle Xcode:
xcode-select --install
or
git config --global --list
Then restart RStudio.