prevent push of irrelevant tags

prevent push of irrelevant tags

[Rolf Leggewie]

Hello,

I just ran into the situation that "git push --tags" pushed tags to the
remote repo that point to commits that do not exist there.  How can this
happen?  Well, in my case it was because I have more than one remote
repo with non-overlapping tags and they cross-polluted each other. 
Another possibility that comes to mind is local tags for
work-in-progress commits, for example.

Git has the information to know that tag X will be useless in repo Y
because the commit Z it points to does not exist in Y.  It would be nice
if "git push --tags" did the right thing and excluded irrelevant tags
when pushing.  Thank you for your attention and thank you for git!

Regards

Rolf

Re: prevent push of irrelevant tags

[Junio C Hamano]

Rolf Leggewie <foss@rolf.leggewie.biz> writes:

> I just ran into the situation that "git push --tags" pushed tags to the
> remote repo that point to commits that do not exist there.  How can this
> happen?

The "--tags" option is to request to push every ref under refs/tags/
hierarchy, so the answer is "because the user asked to".

> Git has the information to know...

No, it doesn't.  

>  that tag X will be useless in repo Y
> because the commit Z it points to does not exist in Y.

Think of a case where:

 1. You have cloned from your origin.

 2. You built history on top of your 'master' branch, and pushed the
    result. The 'master' at your origin now points at this commit.

 3. Somebody working on the project cloned from the same origin, built
    some history, and pushed the result.  The 'master' at your origin is
    again updated to point at this commit (which is a descendant of the
    commit you made in #2).

 4. You tagged the tip of your 'master' as v1.0.

 5. You give the magic "--relevant-tags-only" option to your "git push".

Now what happens?

The only two things your "git push" knows are that your origin does not
have v1.0 tag, and that its 'master' branch points at the commit created
by somebody else at #3.  Most importantly, it does not have the history
leading to this commit ("push" never fetches); it does not have a way to
tell if it is a descendant of commit you created in #2.  In other words,
the magic "--relevant-tags-only" is fundamentally flawed as a concept.

Re: prevent push of irrelevant tags

[Rolf Leggewie]

Hamano-San,

thank you very much for the ultra-quick reply and your explanation.

On 13.04.2012 04:07, Junio C Hamano wrote:
>> Git has the information to know...
> 
> No, it doesn't.  
> 
>>  that tag X will be useless in repo Y
>> because the commit Z it points to does not exist in Y.
> 
> Think of a case where:

I am only a simple user so I hope you will not be angry with me if I
misunderstand you.  I believe you are saying that "git push" does not
have the necessary information which I take your word for.  But git
itself surely should know if commit Z is available from repo Y or am I
mistaken?  For example I can do "git log repoY:master|grep $ZcommitID".
 That would return empty if the master branch at repoY didn't have
information about Z*.

Thank you for bearing with me.

Regards

Rolf


* Of course, it's possible that Z is not part of master but another
  branch at Y.

Re: prevent push of irrelevant tags

[Andreas Schwab]

Rolf Leggewie <foss@rolf.leggewie.biz> writes:

> I just ran into the situation that "git push --tags" pushed tags to the
> remote repo that point to commits that do not exist there.  How can this
> happen?

A tag is just a ref like any other.

> Git has the information to know that tag X will be useless in repo Y
> because the commit Z it points to does not exist in Y.

It is not useless.  After you pushed the tag the commit Z it points to
exists now in Y as well.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."