Re: pre-push hook does not get input on non-fast-forward pushes

[Stefan Beller <sbeller@google.com>]

On Mon, Mar 28, 2016 at 2:44 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at> writes:
>
>> I noticed that without an additional --force the pre-push hook does not
>> get any input on stdin if a push would result in non-fast-forward
>> uploads. This is not a problem per se (although I don't get the
>> rationale) but it is undocumented and the latter left me puzzled.
>>
>> (Please keep me in CC since I am not subscribed, thanks)
>
> Thanks (no need to say "please cc me", as that is the norm here).
>
> The pre-push hook is not the only thing that may prevent you from
> pushing a ref update.  As you noticed, non-fast-forward check may
> trigger and decide that a ref is not going to be pushed, and that
> may happen before we call the pre-push hook.
>
>     Information about what is to be pushed is provided on the hook's
>     standard input with lines of the form ...
>
> So when the pre-push is called, the refs that will not fast-forward
> may not be among the "what is to be pushed", hence not reported.
>
> We _could_ add something like this to the documentation, but we do
> not necessarily want to promise that the order of checks to stay
> "internal checks like non-ff check first before pre-push hook", so
> this update may not be an improvement.  The current text conveys
> enough information without making such a promise, but you need to
> read it carefully.
>
> So I dunno.
>
>  Documentation/githooks.txt | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
> index 9ef2469..605ba4d 100644
> --- a/Documentation/githooks.txt
> +++ b/Documentation/githooks.txt
> @@ -201,7 +201,9 @@ does not yet exist the `<remote SHA-1>` will be 40 `0`.  If a ref is to be
>  deleted, the `<local ref>` will be supplied as `(delete)` and the `<local
>  SHA-1>` will be 40 `0`.  If the local commit was specified by something other
>  than a name which could be expanded (such as `HEAD~`, or a SHA-1) it will be
> -supplied as it was originally given.
> +supplied as it was originally given.  A request to update remote ref that has
> +already been rejected for other reasons (e.g. failing to pass a fast-forward
> +test) does not appear in the input.

If we don't want to give promises, s/does not/ may not/ ?

Although that sounds like it is non-deterministic (some occur, some don't,
maybe it depends on $random_reason)

>
>  If this hook exits with a non-zero status, 'git push' will abort without
>  pushing anything.  Information about why the push is rejected may be sent
>
>
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