Re: [PATCH] Do check_repository_format() early

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Dec 3, 2007, 14:04 UTC
Message-ID: <fcaeb9bf0712030604o2efc90d0m148d3280aaa475a5@mail.gmail.com>
In-Reply-To: <7v4pf25jiq.fsf@gitster.siamese.dyndns.org>

On Dec 2, 2007 1:58 AM, Junio C Hamano <gitster@pobox.com> wrote:

Show 19 quoted lines

>  * Similarly, run a few commands in modes that do not require git
>    repository.  For example, "git apply --stat" of an existing patch
>    should be viewable no matter where you are (that is just a "better
>    diffstat" mode), so ideally it should not barf only because you
>    happen to be in a repository that is too new for you to understand.
>    I do not know offhand how your patch would handle this situation.
>
> Note that making sure the latter works is tricky to do right, for a few
> reasons.
>
>  (1) It is not absolutely clear what the right behaviour is.  It could
>      be argued that we should just barf saying we found a repository we
>      do not understand, refraining from doing any damange on it [*2*].
>
>  (2) If we choose not to barf on such a repository, it remains to be
>      decided what "gently" should do --- if it should still treat
>      t/trash/test (which has too new a version) as the found repository,
>      or ignore it and use t/trash (which we can understand) as the found
>      repository.  I think it should do the former.

You might have forgotten the third choice: ignore t/trash/test and stop searching, instead pretend there is no repository at all (maybe with a big warning of unsupported repository).

I agree t/trash should not be touched no matter what. I had enough "fun" with nested gitdir already. But if _gently() treats t/trash/test as a good repository, mysterious things may happen. Suppose gitdir v2 supports some crazy refspec that current installed git cannot understand. Now you run git-remote on a v2 repository, it would end up barfing "invalid refspec" or something instead of "your repository version is not supported, upgrade git now". The latter error message is much clearer IMHO.

If we are going "t/trash/test is good repo" route, we must make sure _gently() callers check repository version (and barf at proper places) before actually using it. Doing so makes repo version checking in _gently redundant, you need to check it from callers anyway as the callers will decide when to barf. Or return *nongit_ok=-1 and let the callers check return value so they do not need to run check_repository_format_version() again.

Comments?

-- 
Duy