set RStudio to use git bash shell (MINGW64) rather than Rtools (MSYS) shell??

[friendly]

Using RStudio 1.2.5042, Windows 7, R version 3.6.3

When I run shell ... from the Git tab, I get an MSYS terminal window. But there is something wrong because git is not setup properly here. I also have git bash (MINGW64) installed and this works flawlessly, except
I have to navigate separately to the project directory and run Git Bash Here from the explorer menu.

Here's what I see from MSYS:

   friendly@UIT-HHP-31TRNW1 MSYS /c/R/Rprojects/HistDataVis (master)
   $ git commit -m "fix large image file problems"

   *** Please tell me who you are.

   Run

     git config --global user.email "you@example.com"
     git config --global user.name "Your Name"

   to set your account's default identity.
   Omit --global to set the identity only in this repository.

   fatal: unable to auto-detect email address (got 'friendly@UIT-HHP-31TRNW1.(none)
   ')

   friendly@UIT-HHP-31TRNW1 MSYS /c/R/Rprojects/HistDataVis (master)
   $ git add .

   friendly@UIT-HHP-31TRNW1 MSYS /c/R/Rprojects/HistDataVis (master)
   $ git config --global user.email "friendly@yorku.ca"
   error: could not lock config file =/.gitconfig: No such file or directory

Can I change an option in RStudio to use MINGW64?
Can I re-configure MSYS so that it works?