Revert "[upgrader] do not use git for untracked files"
Revert "[upgrader] do not use git for untracked files"

This reverts commit feaa6df7aaa89d8c86e4eae90afb2297ec610db5.

Signed-off-by: Rudi Grinberg <4c46c202a3b8207ad5740134b125aae40c6c67a8@gmail.com>

janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder