"git tag --force" mentions what old tag object is being replaced
when it is used to update an existing tag, but it shows the same
message when creating a new one. Stop doing that, as it does not
add any information.
Add a test for this and also to ensure --force can replace tags at
all.
Signed-off-by: Phil Hord <hordp@cisco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>