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Re: Deprecating git diff ..; dealing with other ranges

Hi Denton,

On Mon, 11 Mar 2019, Denton Liu wrote:

> I was in the process of deprecating `git diff <commit>..<commit>` as
> discussed here[1]. However, I ran into a weird case that I'm not sure
> how to deal with.
> In t3430-rebase-merges.sh:382, we have the following test case which
> invokes git diff:
> 	test_expect_success 'with --autosquash and --exec' '
> 		git checkout -b with-exec H &&
> 		echo Booh >B.t &&
> 		test_tick &&
> 		git commit --fixup B B.t &&
> 		write_script show.sh <<-\EOF &&
> 		subject="$(git show -s --format=%s HEAD)"
> =>		content="$(git diff HEAD^! | tail -n 1)"
> 		echo "$subject: $content"
> 		EOF
> 		test_tick &&
> 		git rebase -ir --autosquash --exec ./show.sh A >actual &&
> 		grep "B: +Booh" actual &&
> 		grep "E: +Booh" actual &&
> 		grep "G: +G" actual
> 	'
> It gets caught in my attempt to only deprecate ..'s. Technically, it's
> undocumented behaviour and it only happens to work because git-diff
> accept ranges but it doesn't operate in an intuitive way.

I beg to differ. `git diff <commit>^!` does exactly what I want: it shows
the diff between the commit's first parent and the commit.

And I would not necessarily call this a "range". It is a short-hand. Can't
you allow short-hands in `git diff`, and disallow only ranges that have an
explicit `..` in them? You might need to record that somewhere, but I
think that should be easy enough.


> I was just wondering what we should do about this case? Should we
> deprecate all invocations of `git diff <range>` except for the special
> case of `git diff <commit>...<commit>`, or should we _only_ deprecate
> `git diff <commit>..<commit>` and allow all other forms of ranges, even
> though it was undocumented behaviour?
> Thanks,
> Denton
> [1]: https://public-inbox.org/git/xmqqmumy6mxe.fsf@xxxxxxxxxxxxxxxxxxxxxxxxx/