Junio C Hamano <gitster@xxxxxxxxx> writes:
> On Fri, Jul 1, 2016 at 3:08 PM, Philip Oakley <philipoakley@xxxxxxx> wrote:
>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>> To exclude commits reachable from a commit, a prefix '{caret}'
>>>> notation is used. E.g. '{caret}r1 r2' means commits reachable
>>>> -from 'r2' but exclude the ones reachable from 'r1'.
>>>> +from 'r2' but exclude 'r1' and those reachable from 'r1'.
>>>
>>> Well, if you have to spell that out, you'd want to spell out r2 side
>>> too, no? That is,
>>
>> The clarification wasn't about what "reachable" means but about inclusivity,
>> such as whether 0..4 would give 0,1,2,3,4 or would be 'off by one' and only
>> give 1,2,3,4. And in this case it's the latter.
>
> Well, you have the same inclusivity issue on the opposite end, no? Is 0..4
> a range with 0,1,2,3,4? 0,1,2,3? 1,2,3,4? or 1,2,3?
>
>> Describing 'reachability' is a whole different kettle of fish, as you
>> highlight below, and would be separate from this patch.
>
> I am not sure I agree. It all is about "is the endpoint included or not?".
This did not come out as illustrating as I hoped. Let's put it
differently.
I think this is all about how "reachable" is defined. "Am I an
ancestor of myself?" is the question.
If "all commits reachable from r1" includes 'r1', then, it is clear
that "... but exclude those reachable from 'r1'" means 'r1' is not
part of the resulting set.
If I were not an ancestor of me, on the other hand, "... but exclude
those who are ancestors of 'r1'" would not exclude 'r1'. If 'r1' is
reachable from 'r2', then 'r1' would be in the resulting set.
The same thing happens at the opposite end of the "range". If I am
an ancestor of me, then "all commits reachable from 'r2'" does
inculde 'r2'; if I am not an ancestor of me, 'r2' is not part of the
resulting set.
Note. I said "range" in quotes, because this is not like
drawing a straight line and placing two points to denote the
lower and the upper bounds of the "range". What Git does is
a set operation, "r2 ^r1" excludes what is reachable from r1
from the set of commits that are reachable from r2.
By choosing the definition of "reachable" consistently, 0..4 can
mean either 1,2,3,4 (I am reachable from myself) or 0,1,2,3 (I can
not be reached by me), and in order to clarify that we give 1,2,3,4
and not 0,1,2,3, we still need to clearly define what "reachable"
means.
But any other interpretation, e.g. 0,1,2,3,4, is incoherent.
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