Re: [PATCH v3] Simplify handling of setup_git_directory_gently() failure cases.

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 3, 2019, 18:09 UTC
Message-ID: <xmqqy381haup.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20190103051432.GE20047@sigill.intra.peff.net>

>Subject: Re: [PATCH v3] Simplify handling of setup_git_directory_gently() failure cases.

Perhaps

	Subject: setup: simplify setup_git_directory_gently() failure cases

to clarify which part of the entire world this patch is touching.

Jeff King <peff@peff.net> writes:

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> This patch isn't _too_ big, so I don't think it's worth the effort at
> this point for this particular case, but just something to think about
> for the future. A series around this topic would probably be something
> like:
>
>   1: drop the useless chdir and fold setup_nongit() into the main
>      function
>
>   2: stop doing the early return from HIT_MOUNT_POINT, and treat it just
>      like HIT_CEILING (and drop the useless strbuf release)
>
>   3: treat GIT_DIR_NONE as a BUG
>
>   4: rearrange the nongit logic at the end of the function for clarity

Yeah, that organization does make sense. And I agree with your rule of thumb to use the length and complexity of the log message to judge if a single step is getting too big.

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> We usually avoid "//" comments, even for single lines (though that is
> perhaps superstition at this point, as we've started to embrace several
> other C99-isms). IMHO this particular comment is not even really
> necessary, as the whole conditional is suitably short and obvious after
> your refactor.

FWIW "git grep" for // seems to show that we reserve use of // inside commented out code samples.

I also agree the comments behind // in this patch are probably unneeded.

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>
>> @@ -1132,7 +1142,10 @@ const char *setup_git_directory_gently(int *nongit_ok)
>>  	 * the user has set GIT_DIR.  It may be beneficial to disallow bogus
>>  	 * GIT_DIR values at some point in the future.
>>  	 */
>> -	if (startup_info->have_repository || getenv(GIT_DIR_ENVIRONMENT)) {
>> +	if (// GIT_DIR_EXPLICIT, GIT_DIR_DISCOVERED, GIT_DIR_BARE
>> +	    startup_info->have_repository ||
>> +	    // GIT_DIR_EXPLICIT
>> +	    getenv(GIT_DIR_ENVIRONMENT)) {
>
> Same "//" style issue as above. I'm not sure how much value there is in
> repeating the GIT_DIR_* cases here, as they're likely to grow out of
> sync with the switch() statement above.

It is unclear to me if the original code is doing the right thing under one condition, and this patch does not seem to change the behaviour.

What happens if GIT_DIR environment is set to an invalid path and nongit_ok is non-NULL? setup_explicit_git_dir() would have assigned 1 to *nongit_ok, so have_repository is false at this point.

We enter the if() statement in such a case, and end up calling setup_git_env(gitdir) using the bogus path that is not pointing at a repository. We leave have_repository to be false but the paths recorded in the_repository by setup_git_env() would all point at bogus places.

> At first I thought this could all be folded into the "else" clause of
> the conditional above (which would make the logic much easier to
> follow), but that wouldn't cover the case of GIT_DIR=/bogus, which is
> what that getenv() is trying to handle here.

Yes, but should GIT_DIR=/bogus even be touching the_repository?

It is a separate clean-up and does not affect the validity of this simplification patchd, so I agreee with ...

> So I think this is the best we can do for now.

Thanks.