Re: [PATCH v2 2/3] add -p: allow line selection to be inverted

> Phillip Wood <phillip.wood@talktalk.net> writes:
> 
>> On 08/03/18 17:53, Junio C Hamano wrote:
>>> Phillip Wood <phillip.wood@talktalk.net> writes:
>>>
>>>> and use a leading '-' for inversion. I'm tempted to keep supporting 'n-'
>>>> to mean everything from 'n' to the last line though.
>>>
>>> Thanks for double checking.  It would be a better endgame to follow
>>> up with an update to existing "range selection" code to also support
>>> "n-", if you go that route.
>>>
>> I'm afraid I'm not sure exactly what you're suggesting. At the moment
>> the range selection code is in the first patch and supports incomplete
>> ranges. Are you suggesting that support for incomplete ranges should be
>> in a separate patch or have I misunderstood?
> 
> My observation of the situation behind my reasoning is:
> 
>  - There is an existing UI that uses "-X" to mean "exclude what
>    matches X" and that was the reason why you decided to follow suit
>    instead of using "^X" for inversion of X.
> 
>  - Such an existing UI would not have used "-X" to mean "the first
>    possible choice thru X".  You will lose that from your new thing
>    and you accepted that.
> 
>  - It is likely (I did not check, though) that the existing UI would
>    not have used "Y-" to mean "starting from Y all the possible
>    choices thru to the end", but that is merely for symmetry with
>    the lack (inability to use) of "-X".  There is no fundamental
>    reason why "Y-" cannot mean that, and you are tempted to allow do
>    so in your new thing for the same reason.
> 
> So if we are going to have "N-" to mean "everything from N to the
> last line", then the same "Starting at N to the end of the all the
> possible choices" should be allowed in the existing UI (i.e. the one
> that forced you to give up "^X" for the sake of consistency) for the
> same consistency reasons, no?
> 
> For that, if you want to keep the "n-" you did in your first patch,
> the most logical thing is to have a preparatory enhancement to teach
> "N-" to list_and_choose(), and then build your series on top.  Or
> you can do without such a change to list_and_choose() in your series,
> in which case, you drop "n-" support and then at the very end after
> the series settles, add "n-" support to the new code in this series
> and to list_and_choose() at the same time in a follow-up patch.
> 
>