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

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 28, 2016, 21:44 UTC
Message-ID: <xmqq1t6uxop7.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <201603282056.u2SKuqDf031459@mail2.student.tuwien.ac.at>

Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at> writes:

Show 6 quoted lines

> 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 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