"J. Bruce Fields" <bfields@xxxxxxxxxxxx> writes:
> On Mon, Apr 28, 2008 at 12:28:38PM -0700, Linus Torvalds wrote:
>>
>>
>> On Mon, 28 Apr 2008, Johannes Schindelin wrote:
>>>
>>> On Mon, 28 Apr 2008, Andrew Morton wrote:
>>>>
>>>> That's missing the "logical" bit :)
>>>
>>> Heh, you're right. I am too used to Git to think how other people would
>>> feel about these things... :-)
>>
>> No, you are both wrong.
>>
>> You're wrong because apparently you never did abstract algebra and set
>> theory in school.
[...]
>> If you know math, git actually does the rigth and very much the *logical*
>> thing.
>>
>> So ".." is a simple difference, while "..." is a more complex difference.
>>
>> They mean different things for different operation types, but that is
>> again something a math person takes for granted (ie in algebra, a "+" or
>> "-" is just a random operation that follows certain rules: "a-b" means one
>> thing for the set of real numbers, and something *totally* different if
>> you are talking about set algebra).
[...]
> I can sorta buy the argument that "A...B" means most generally "some
> kind of difference between the three sets A, A^B, and B", and that in
> the context of "git diff" it's most sensible to take ordering into
> account and produce some approximation of a diff between A^B and B. I'd
> personally have found an entirely separate operator simpler to
> understand. But perhaps there's only so many keys on the keyboard.
IMHO adding support for a..b and a...b to git-diff is a bit of trick,
as a..b and a...b were created to represent a set of revisions (a
revision range).
If we have linear history:
*---*---*---a---*---*---b
then a..b notation for a revision range is very natural, and having
git-diff interprete "a..b" as "a b" (for git-diff only endpoints
matter) to allow copy'n'pasting between git-log and git-diff, and
between git-fetch messages and git-diff was a good extension.
Now if the history is not linear, as in example below:
*---*---*---x---*---*---b
\
\-*---a
then "a..b", which is shortcut for "b ^a" (b --not a), returns x..b
range (set) of revisions. If you read "a..b" as "what's in 'b'
since 'a'" it makes perfect sense. But "git diff a..b" is still
"git diff a b", not "git diff x b".
It would be perhaps as good notation to have "git diff a..b" mean
"git diff x b", i.e. be diff between endpoints of "git log a..b",
and have "git diff a...b" be "git diff a b", i.e. to be diff between
endpoints^W points of "git log a...b"... but if there is no clean
winner, simplicity of implementation wins.
--
Jakub Narebski
Poland
ShadeHawk on #git
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