Re: Strange annotated tag issue

[Robert Dailey <rcdailey.lists@gmail.com>]

On Thu, Mar 21, 2019 at 2:29 PM Jeff King <peff@peff.net> wrote:
> Tags can point to any object, including another tag. It looks like
> somebody made an annotated tag of an annotated tag (probably by
> mistake, given that they have the same tag-name).
>
> Try this:
>
>   git init
>   git commit -m commit --allow-empty
>   git tag -m inner mytag HEAD
>   git tag -f -m outer mytag mytag
>
>   git show mytag
>
> which produces similar output. You can walk the chain yourself with "git
> at-file tag 4.2.0.1900". That will have a "type" and "object" field
> which presumably point to the second commit.
>
> My guess is that somebody was trying to amend the tag commit message,
> but used the tag name to create the second one, rather than the original
> commit. I.e,. any of these would have worked for the second command to
> replace the old tag:
>
>   git tag -f -m 'new message' mytag HEAD
>
>   git tag -f -m 'new message' 2fcfd00ef84572fb88852be55315914f37e91e11
>
>   git tag -f -m 'new message' mytag mytag^{commit}
>
> If the original tag isn't signed, you could rewrite it at this point
> using one of the above commands, coupled with GIT_COMMITTER_* to munge
> the author and date.  But note that fetch doesn't update modified tags
> by default, so it may just cause confusion if you have a lot of people
> using the repository.

Thanks for explaining. This is very helpful. Am I naive to think that
this should be an error? I haven't seen a valid _pragmatic_ use for
tags pointing to tags. In 100% of cases (including this one), it is
done out of error. As per your example, users try to "correct" an
annotated tag pointing at a wrong tag or commit. What they expect is
the tag to point to the other tag's commit, but that's not what they
get.

From a high-level, pragmatic perspective, doesn't it make more sense
to change the git behavior so that annotated tags may only point to
commit objects? And in the `git tag -f -m outer mytag mytag` case in
your example, this would automatically perform `mytag^{}` to ensure
that the behavior the user expects is the behavior they get?