Re: [PATCH v2 06/10] push doc: correct lies about how push refspecs work

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 31, 2018, 17:40 UTC
Message-ID: <xmqq8t5rcnhg.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20180731130718.25222-7-avarab@gmail.com>

Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:

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>  The <src> is often the name of the branch you would want to push, but
> -it can be any arbitrary "SHA-1 expression", such as `master~4` or
> -`HEAD` (see linkgit:gitrevisions[7]).
> +it can be any arbitrary expression to a commit, such as `master~4` or
> +`HEAD` (see linkgit:gitrevisions[7]). It can also refer to tag
> +objects, trees or blobs if the <dst> is outside of `refs/heads/*`.

"It can also refer to..." is a good addition, but do you really want to make it part of this series to change/deprecate "SHA-1 expression" (which would certainly involve discussion on "then what to call them instead, now we are trying to refrain from saying SHA-1?")?

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> +on the remote side. Whether this is allowed depends on where in
> +`refs/*` the <dst> reference lives. The `refs/heads/*` namespace will
> +only accept commit objects, and then only they can be
> +fast-forwarded. The `refs/tags/*` namespace will accept any kind of
> +object, and any changes to them and others types of objects will be
> +rejected. Finally, it's possible to push any type of object to any
> +namespace outside of `refs/{tags,heads}/*`,

All sound correct.

> but these will be treated
> +as branches for the purposes of whether `--force` is required, even in
> +the case where a tag object is pushed.

I am not sure what "will be treated as branches" exactly means. Does it mean "as if they were in refs/heads/* hierarchy?" Or something else?

> That tag object will be
> +overwritten by another tag object (or commit!) without `--force` if
> +the new tag happens to point to a commit that's a fast-forward of the
> +commit it replaces.

Yup, and that is something we want to fix with a later part of this series.

> +By having the optional leading `+` to a refspec (or using `--force`
> +command line option) you can tell Git to update the <dst> ref even if
> +it is not allowed by its respective namespace clobbering rules (e.g.,
> +it is not a fast-forward. in the case of `refs/heads/*` updates).

This gives an impression that with "--force" you can put non-commit inside refs/heads/* hierarchy. Is that correct (if so we probably would want to fix that behaviour)?

> +This
> +does *not* attempt to merge <src> into <dst>.  See EXAMPLES below for
> +details.

That is not wrong per-se, but would normal people expect a merge to happen upon pushing on the other side, I wonder?

Thanks for cleaning up our longstanding mess.