Re: [PATCH] Documentation: "bisect run" can be given bangs before the run script.

[Christian Couder <chriscool@tuxfamily.org>]

Hi Junio and Uwe,

Le jeudi 3 mai 2007 07:29, Junio C Hamano a écrit :
> I am not convinced that '!' is a good extension for two and half
> reasons.
>
>  * The expected use is not quite clear.  If it is not used to
>    run a custom test script but something stock as "make", by
>    the nature of UNIX exit status convention, you are looking
>    for the commit that _fixed_ some breakage (i.e. "which commit
>    fixed the compilation error?").  While sometimes that is a
>    useful thing to do, it feels somewhat of limited value.

Well, of course the main expected use is for something like "make" or "grep" 
or "./test_something.sh" where "test_something.sh" is an already existing 
script.

Especially because "git bisect run ! grep foo bar.txt" seems to me like a 
nice way to find the commit that introduced "foo" in "bar.txt" and I have 
been frustrated that it does not work. (Perhaps "git blame" can do it too, 
but I think "git bisect run" should be faster and more specific.)

>    On the other hand, if you are running a custom test script, I
>    do not think it is unreasonable to always require that a test
>    script to signal "bad" with small non-zero, "good" with zero,
>    and error with high non-zero status, as we already do.

I agree this is probably the most usefull use of "git bisect run". But 
sometimes, perhaps for a one shot use, you already have something that 
could work if only you could revert the exist status. I think it is a good 
idea to give user some rope for this case.

>  * How should this interact with the "high non-zero status means
>    an error and we cannot bisect" return convention?

If you use a bare "! grep foobar /*/*" on the command line for example and 
you kill it before it's finished, you will still get a 0 exit code. This 
means that, with the bash "!" keyword, any error gives a "good" result. I 
think it's better to keep this behavior.

If we still wants something that keeps the "high non-zero status means an 
error and we cannot bisect" return convention, then let's call it a "--not" 
option or something like that. I will implement that if you prefer. I can 
even implement both "!" and "--not" if you want.

By the way I think that sometimes it could happens that any exit code other 
than 0 means a "bad" revision and not "we cannot bisect". In this case 
using "git bisect run ! ! my_script" can be usefull. 

>  * I was hoping that we can officially support "don't know,
>    cannot test this one, please give me another" for interactive
>    use, and at the same time allow the run-script used by
>    "git bisect run" to signal such with a special exit value
>    (perhaps "exit 42").  Taken together with the previous point,
>    it is not clear how '!' should interact with such an
>    enhancement.

My bang patch does not in any way prevents from adding such a "don't know, 
cannot test this one, please give me another" improvement. It's just 
another option to make "git bisect run" more convenient in some cases.

Christian (a give them rope proponent).