Re: Git fails to detect subcommand when hook is symlinked to a builtin

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 19, 2011, 00:53 UTC
Message-ID: <7vhbb0rkv4.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20110318151415.GC26236@inocybe.localdomain>

Todd Zullinger <tmz@pobox.com> writes:

Show 7 quoted lines

> I'm not sure if this is a bug or more of a "don't do that" sort of
> thing.  At fedorahosted.org, the git repositories are mounted on a
> filesystem with noexec.  As such, we have all hooks symlinked
> elsewhere.  For the post-update hook we used to link directly to
> git-update-server-info.
>
> This worked until we upgraded the system to git-1.7.4.1 recently.

I have a suspicion that we may end up saying "don't do that", but let's ponder a bit with some technical background first. The "git" wrapper and builtin commands are all the same binary, and as a consequence, their main() function needs to decide what to do based on argv[0]. If argv[0] is "git", we know argv[1] is the name of the subcommand, and if argv[0] is "git-foo", it might be the internal call from the "git" wrapper that was invoked with argv[] = { "git", "foo", ... }, but we don't expect that argv[0] to be things like "post-update".

But it is curious why the resulting behaviour changed recently. The symptom hints that the link target (git-update-server-info in your case) used to be given as argv[0] (which still wouldn't have been kosher---you are not supposed to use dashed form since 1.5.4 or so without adding $GIT_EXEC_PATH at the beginning of your $PATH, and that is why I said the first sentence in this reply), but we recently changed something and now we are getting "hooks/post-update" in argv[0].

I suspect the recent change to run hooks via run_command() interface has something to do with it. From what version did you update to 1.7.4.1?