Re: [PATCH v3 1/5] t4001: add a test comparing basename similarity and content similarity

From: Junio C Hamano <gitster@pobox.com>
Date: Feb 13, 2021, 01:15 UTC
Message-ID: <xmqq4kigvkct.fsf@gitster.c.googlers.com>
In-Reply-To: <3e6af929d135ef2dc239e2f47f92a7e2e91cbd17.1612970140.git.gitgitgadget@gmail.com>

"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 8 quoted lines

> From: Elijah Newren <newren@gmail.com>
>
> Add a simple test where a removed file is similar to two different added
> files; one of them has the same basename, and the other has a slightly
> higher content similarity.  Without break detection, filename similarity
> of 100% trumps content similarity for pairing up related files.  For
> any filename similarity less than 100%, the opposite is true -- content
> similarity is all that matters.  Add a testcase that documents this.

I am not sure why it is the "opposite". When contents are similar to the same degree of 100%, we tiebreak with the filename. We never favor a pair between the same filename over a pair between different filenames with better content similarity.

And when contents are similar to the same degree of less than 100%, we do not favor a pair between the same filename over a pair between different filenames, as long as they are similar to the same degree.

So, I do not think "opposite" is helping readers to understand what is going on.

Show 17 quoted lines

> +test_expect_success 'basename similarity vs best similarity' '
> +	mkdir subdir &&
> +	test_write_lines line1 line2 line3 line4 line5 \
> +			 line6 line7 line8 line9 line10 >subdir/file.txt &&
> +	git add subdir/file.txt &&
> +	git commit -m "base txt" &&
> +
> +	git rm subdir/file.txt &&
> +	test_write_lines line1 line2 line3 line4 line5 \
> +			  line6 line7 line8 >file.txt &&
> +	test_write_lines line1 line2 line3 line4 line5 \
> +			  line6 line7 line8 line9 >file.md &&
> +	git add file.txt file.md &&
> +	git commit -a -m "rename" &&
> +	git diff-tree -r -M --name-status HEAD^ HEAD >actual &&
> +	# subdir/file.txt is 89% similar to file.md, 78% similar to file.txt,
> +	# but since same basenames are checked first...

I am not sure what the second line of this comment wants to imply with the ellipses here. Care to finish the sentence?

Or was the second line planned to be added when we start applying the "check only the same filename first and see if we find a better-than-reasonable match" heuristics but somehow survived "rebase -i" and ended up here?

Show 5 quoted lines

> +	cat >expected <<-\EOF &&
> +	R088	subdir/file.txt	file.md
> +	A	file.txt
> +	EOF
> +	test_cmp expected actual

Thanks.