Re: [PATCH] diff: add --ignore-blank-lines option

[Junio C Hamano <gitster@pobox.com>]

Antoine Pelisse <apelisse@gmail.com> writes:

> On Tue, Jun 4, 2013 at 8:26 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> Antoine Pelisse <apelisse@gmail.com> writes:
>>
>>> +xdchange_t *xdl_get_hunk(xdchange_t **xscr, xdemitconf_t const *xecfg) {
>>>       xdchange_t *xch, *xchp;
>>>       long max_common = 2 * xecfg->ctxlen + xecfg->interhunkctxlen;
>>> +     long ignorable_context = max_common / 2 - 1;
>>
>> Could you explain how this math works?
>
> I think it doesn't, mostly because I misinterpreted the "interhunkctxlen".
> I will try to think about that and provide a reroll.

OK.  Thanks.

I think the logic would be more like:

 1. Start from xscr, find the first xchp that is !xchp->ignore;
    if there is none, we are done. There is no more to show.

 2. Remember the xchp as the beginning.

 3. Tangle ->next pointer to find the next xch that is !xch->ignore;
    if there is none, we are also done.  xdchanges between the
    beginning you remembered in the step 2. and your current xchp
    are the only things we want to show.

 4. Measure the distance between the end of xchp and the beginning
    of xch.

    - If it is larger than max_common, xdchanges between the
      beginning you remembered in the step 2. and your current xchp
      are the only things we want to show.  The next iteration will
      start by skipping the blank-only changes between xchp and xch.

    - If it is short enough, assign xchp = xch and go back to 3. to
      find more interesting hunks (that is why we remembered the
      real "beginning" in step 2.).