Re: [PATCH] BreakingChanges: say that `git diff X..Y` syntax will be removed in 3.0

From: Martin von Zweigbergk <martinvonz@google.com>
Date: Oct 16, 2025, 16:34 UTC
Message-ID: <CAESOdVDbVDwmYOFRAAC07GXaJ871FiPWTx58YMLta7vAWDjgfw@mail.gmail.com>
In-Reply-To: <i5lgq7cunzqn2k3puuudzb53efqz6cxev64l6ukwy2kf24dab3@ndymfd2ocit3>

On Wed, 15 Oct 2025 at 18:28, Justin Tobler <jltobler@gmail.com> wrote:

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>
> On 25/10/15 10:07PM, Martin von Zweigbergk via GitGitGadget wrote:
> > From: Martin von Zweigbergk <martinvonz@google.com>
> >
> > The `git diff X..Y` syntax is quite misleading because it looks like
> > it shows the diff of the commits in the X..Y range but it actually
> > shows the diff from X to Y.
>
> Personally, I would like to see both the double-dot and triple-dot
> notations removed from the diff commands because they are often confused
> with the revision range notations.

Oh, I agree. I had forgotten that the triple-dot notation is also accepted.

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> In my opinion, the double-dot
> notation doesn't even have much value as it can be replaced with:
>
>   A..B => A B
>   A..  => A @
>    ..B => @ B
>
> These alternatives are just as concise.
>
> > IMO, if that syntax is supported, it
> > should show a diff from the merge base of X and Y to Y. I hope Git 3.0
> > is a good time to remove support for the current syntax and
> > semantics. Then we can perhaps add the syntax back later with less
> > surprising semantics.
>
> With the existing triple-dot notation, `git diff A...B` is equivalent to
> `git diff $(git merge-base A B) B`. I think this is what you are
> suggesting about that the double-dot notation should do. As mentioned
> earlier, I think both these notations are too easily confused with
> revision range notations so I think we should avoid using the dot syntax
> for such a shortcut altogether.

FWIW, `jj diff` can diff between two commits with `jj diff --from A --to B`. It can also show the changes in commit A with `jj diff -r A`. You can also show the combined diffs in a range with `jj diff -r A..B` (i.e. `jj diff -r A` is a special case of that). I think that's consistent with the range notation because it's the same set of commits that are considered. But both `git diff A..B` and `git diff A...B` take range expressions and show diffs that don't correspond to those ranges. So I guess I'm saying that I'm not fundamentally opposed to having a way of showing the combined diff in a range, as long as it's consistent.

>
> The triple-dot notation is a somewhat convienient shortcut though. If we
> wanted to remove it, we would maybe want to replace it some other
> functionally equivalent shortcut.

Makes sense. The problem is that there are not many symbols that are available without requiring shell escaping. I don't have a good suggestion.

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>
> All this being said, I've sure there are folks in the wild using these
> notations in scripts and changing would cause disruption. Maybe the Git
> 3.0 release would indeed be a good time to remove them though.
>
> -Justin