Re: [PATCH v3] ref-filter: fallback on alphabetical comparison

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 27, 2015, 19:50 UTC
Message-ID: <xmqq7fm8ozu9.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <1445972456-5621-1-git-send-email-Karthik.188@gmail.com>

Karthik Nayak <karthik.188@gmail.com> writes:

Show 6 quoted lines

> In ref-filter.c the comparison of refs while sorting is handled by
> cmp_ref_sorting() function. When sorting as per numerical values
> (e.g. --sort=objectsize) there is no fallback comparison when both
> refs hold the same value. This can cause unexpected results (i.e. the
> order of listing refs with equal values cannot be pre-determined) as
> pointed out by Johannes Sixt ($gmane/280117).

As we use qsort(), if two members compare as equal, their order in the sorted array is undefined. I think this is a good change.

> Hence, fallback to alphabetical comparison based on the refname
> whenever the other criterion is equal. Fix the test in t3203 in this
> regard.

It is unclear what "in this regard" is. Do you mean this (I am not suggesting you to spell these out in a very detailed way in the final log message; I am deliberately being detailed here to help me understand what you really mean)?

    A test in t3203 was expecting that branch-two sorts before HEAD,
    which happened to be how qsort(3) on Linux sorted the array, but
    (1) that outcome was not even guaranteed, and (2) once we start
    breaking ties with the refname, "HEAD" should sort before
    "branch-two" so the original expectation was inconsistent with
    the criterion we now use.

    Update it to match the new world order, which we can now depend
    on being stable.

I am not sure about "HEAD" and "branch-two" in the above (it may be comparison between "HEAD" and "refs/heads/branch-two", for example).

Show 34 quoted lines

> Reported-by: Johannes Sixt <j6t@kdbg.org>
> Signed-off-by: Karthik Nayak <Karthik.188@gmail.com>
> ---
>  ref-filter.c             | 2 +-
>  t/t3203-branch-output.sh | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/ref-filter.c b/ref-filter.c
> index 046e73b..7b33cb8 100644
> --- a/ref-filter.c
> +++ b/ref-filter.c
> @@ -1698,7 +1698,7 @@ static int cmp_ref_sorting(struct ref_sorting *s, struct ref_array_item *a, stru
>  		if (va->ul < vb->ul)
>  			cmp = -1;
>  		else if (va->ul == vb->ul)
> -			cmp = 0;
> +			cmp = strcmp(a->refname, b->refname);
>  		else
>  			cmp = 1;
>  	}
> diff --git a/t/t3203-branch-output.sh b/t/t3203-branch-output.sh
> index f77971c..9f2d482 100755
> --- a/t/t3203-branch-output.sh
> +++ b/t/t3203-branch-output.sh
> @@ -158,8 +158,8 @@ EOF
>  
>  test_expect_success 'git branch `--sort` option' '
>  	cat >expect <<-\EOF &&
> -	  branch-two
>  	* (HEAD detached from fromtag)
> +	  branch-two
>  	  branch-one
>  	  master
>  	EOF