Re: git push tags

[Jeff King <peff@peff.net>]

On Mon, Oct 29, 2012 at 06:23:30PM +0100, Kacper Kornet wrote:

> > That patch just blocks non-forced updates to refs/tags/. I think a saner
> > start would be to disallow updating non-commit objects without a force.
> > We already do so for blobs and trees because they are not (and cannot
> > be) fast forwards. The fact that annotated tags are checked for
> > fast-forward seems to me to be a case of "it happens to work that way"
> > and not anything planned. Since such a push drops the reference to the
> > old version of the tag, it should probably require a force.
> 
> I'm not sure. Looking at 37fde87 ("Fix send-pack for non-commitish
> tags.") I have an impression that Junio allowed for fast-forward pushes
> of annotated tags on purpose.

Hmm. You're right, though I'm not sure I agree with the reasoning of
that commit. I'd certainly like to get Junio's input on the subject.

> > Then on top of that we can talk about what lightweight tags should do.
> > I'm not sure. Following the regular fast-forward rules makes some sense
> > to me, because you are never losing objects. But there may be
> > complications with updating tags in general because of fetch's rules,
> > and we would be better off preventing people from accidentally doing so.
> > I think a careful review of fetch's tag rules would be in order before
> > making any decision there.
> 
> The problem with the current behaviour is, that one can never be 100% sure
> that his push will not overwrite someone else tag.

Yes, although you do know that you are not throwing away history if you
do (because it must be a fast forward). Whereas if you have to use "-f"
to update a tag, then you have turned off all safety checks. So it is an
improvement for one case (creating a tag), but a regression for another
(updating an existing tag). I agree that the latter is probably less
common, but how much? If virtually nobody is doing it because git-fetch
makes the fetching side too difficult, then the regression is probably
not a big deal.

-Peff