if we run

git add -A

inside sub-directory, it will stage all of the changes even though some of the changes are up one directory. But

git add .

will only stage all updated, deleted and new files that are inside the sub-directory If we are inside

my_dir

sub-directory, the two commands will do the same

git add .  /  git add -A my_dir/

https://youtu.be/tcd4txbTtAY?t=349