Subject: Re: [PATCH] apply: support case-only renames in case-insensitive filesystems

From: Junio C Hamano <[email-masked]>
Date: Sun, 12 Jun 2022 16:30:12 -0700

"Tao Klerks via GitGitGadget" <[email-masked]> writes:

> +if ! test_have_prereq CASE_INSENSITIVE_FS
> +then
> +	test_set_prereq CASE_SENSITIVE_FS
> +	echo nuts
> +fi

You can easily say !CASE_INSENSITIVE_FS as the prerequiste, so I do
not see the point of this.  I do not see the point of "nuts", either.

But it probably is a moot point as I do not think you should do the
prerequisite at all.

Instead, you can explicitly set the core.ignorecase configuration,
i.e. "git -c core.ignorecase=yes/no", and possibly "apply --cached"
so that you do not have to worry about the case sensitivity of the
filesystem at all.

> +test_expect_success setup '
> +	echo "This is some content in the file." > file1 &&

Style.  Redirection operator ">" sticks to its operand, i.e.

	echo "This is some content in the file." >file1 &&

> +	echo "A completely different file." > file2 &&
> +	git update-index --add file1 &&
> +	git update-index --add file2 &&
> +	cat >case_only_rename_patch <<-\EOF
> +	diff --git a/file1 b/File1
> +	similarity index 100%
> +	rename from file1
> +	rename to File1
> +	EOF

You are better off not writing the diff output manually.  Instead,
you can let the test write it for you, e.g.

	echo "This is some content in the file." >file1 &&
	git update-index --add file1 &&
        file1blob=$(git rev-parse :file1) &&
	git commit -m "Initial - file1" &&
	git update-index --add --cacheinfo 100644,$file1blob,File1 &&
	git rm --cached file1 &&
	git diff --cached -M HEAD >case-only-rename-patch

If you want to be extra careful not to rely on your filesystem
corrupting the pathnames you feed (e.g. the redireciton to "file1"
might create file FILE1 on MS-DOS ;-), you could even do:

	file1blob=$(echo "This is some content in the file." |
		    git hash-object -w --stdin) &&
	file2blob=$(echo "A completeloy different contents." |
		    git hash-object -w --stdin) &&
	git update-index --add --cacheinfo 100644,$file1blob,file1 &&

	git commit -m "Initial - file1" &&
	git update-index --add --cacheinfo 100644,$file1blob,File1 &&
	git rm --cached file1 &&
	git diff --cached -M HEAD >rename-file1-to-File2 &&

	git reset --hard HEAD &&
        git update-index --add --cacheinfo 100644,$file1blob,file2 &&
	git rm --cached file1 &&
	git diff --cached -M HEAD >rename-file1-to-file2 &&

	# from here on, HEAD has file1 and file2
	git reset --hard HEAD &&
	git update-index --add --cacheinfo 100644,$file2blob,file2 &&
	git commit -m 'file1 and file2'

> +'
> +
> +test_expect_success 'refuse to apply rename patch with conflict' '
> +	cat >conflict_patch <<-\EOF &&
> +	diff --git a/file1 b/file2
> +	similarity index 100%
> +	rename from file1
> +	rename to file2
> +	EOF
> +	test_must_fail git apply --index conflict_patch

And then, you could use --cached (not --index) to bypass the working
tree altogether, which is a good way to test the feature without
getting affected by the underlying filesystem.  Check both case
sensitive and case insensitive cases:

	# Start from a known state
	git reset --hard HEAD &&
	test_must_fail git -c core.ignorecase=no apply --cached rename-file1-to-file2 &&

	# Start from a known state
	git reset --hard HEAD &&
	test_must_fail git -c core.ignorecase=yes apply --cached rename-file1-to-file2 &&

> +'
> +
> +test_expect_success CASE_SENSITIVE_FS 'refuse to apply case-only rename patch with conflict, in case-sensitive FS' '

Lose the prerequisite, replace --index with --cached, and force core.ignorecase
to both case insensitive and sensitive to check the behaviour.

> +	test_when_finished "git mv File1 file2" &&
> +	git mv file2 File1 &&
> +	test_must_fail git apply --index case_only_rename_patch
> +'
> +
> +test_expect_success 'apply case-only rename patch without conflict' '

Likewise, try both sensitive and insensitive one.

> +	git apply --index case_only_rename_patch
> +'
> +
> +test_done
>
> base-commit: 1e59178e3f65880188caedb965e70db5ceeb2d64

Thanks.