Difference between git add ., git add -A and git add -u [duplicate]

git help add

   -A, --all, --no-ignore-removal
       Update the index not only where the working tree has a file matching <pathspec> but also where the index already has an
       entry. This adds, modifies, and removes index entries to match the working tree.

       If no <pathspec> is given, the current version of Git defaults to "."; in other words, update all files in the current
       directory and its subdirectories. This default will change in a future version of Git, hence the form without <pathspec>
       should not be used.

   -u, --update
       Update the index just where it already has an entry matching <pathspec>. This removes as well as modifies index entries to
       match the working tree, but adds no new files.

       If no <pathspec> is given, the current version of Git defaults to "."; in other words, update all tracked files in the
       current directory and its subdirectories. This default will change in a future version of Git, hence the form without
       <pathspec> should not be used.

• . is implied by both -A and -u if no <pathspec> is given (which is the case in your question).
• -A will stage changes, removed files, and added files.
• -u will stage changes and removed files, but not added files.