git.el: Add an insert file command.
git.el: Add an insert file command.

This allows to insert a file in the buffer no matter what its state
is, making it possible for instance to remove an up-to-date file.

Signed-off-by: Alexandre Julliard <a3c1c71ac0d85b781251f68481a696b8e4d0781d@winehq.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git