Re: [PATCH] git-push: update remote tags only with force

>
> References are allowed to update from one commit-ish to another if the
> former is a ancestor of the latter.  This behavior is oriented to
> branches which are expected to move with commits.  Tag references are
> expected to be static in a repository, though, thus an update to a
> tag (lightweight and annotated) should be rejected unless the update is
> forced.
>
> To enable this functionality, the following checks have been added to
> set_ref_status_for_push() for updating refs (i.e, not new or deletion)
> to restrict fast-forwarding in pushes:
>
>   1) The old and new references must be commits.  If this fails,
>      it is not a valid update for a branch.
>
>   2) The reference name cannot start with "refs/tags/".  This
>      catches lightweight tags which (usually) point to commits
>      and therefore would not be caught by (1).
>
> If either of these checks fails, then it is flagged (by default) with a
> status indicating the update is being rejected due to the reference
> already existing in the remote.  This can be overridden by passing
> --force to git push.
>
> The new status has the added benefit of being able to provide accurate
> feedback as to why the ref update failed and what can be done.
> Currently all ref update rejections are assumed to be for branches.

> +test_expect_success 'push tag requires --force to update remote tag' '
> +       mk_test heads/master &&
> +       mk_child child1 &&
> +       mk_child child2 &&
> +       (
> +               cd child1 &&
> +               git tag lw_tag &&
> +               git tag -a -m "message 1" ann_tag &&
> +               git push ../child2 lw_tag &&
> +               git push ../child2 ann_tag &&
> +               >file1 &&
> +               git add file1 &&
> +               git commit -m "file1" &&
> +               git tag -f lw_tag &&
> +               git tag -f -a -m "message 2" ann_tag &&
> +               ! git push ../child2 lw_tag &&