Subject: Re: [PATCH 2/2] ignorecase: Fix git mv on insensitive filesystems

From: Junio C Hamano <[email-masked]>
Date: Thu, 08 May 2014 12:54:55 -0700

[email-masked] writes:

> From: David Turner <[email-masked]>
>
> Make it possible to change the case of a filename on a
> case-insensitive filesystem using git mv.  Change git mv to allow
> moves where the destination file exists if the destination file has
> the same name as the source file ignoring case.
>
> Signed-off-by: David Turner <[email-masked]>
> ---
>  builtin/mv.c                | 3 ++-
>  t/t6039-merge-ignorecase.sh | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/mv.c b/builtin/mv.c
> index 45e57f3..f4d89d0 100644
> --- a/builtin/mv.c
> +++ b/builtin/mv.c
> @@ -202,7 +202,8 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
>  			}
>  		} else if (cache_name_pos(src, length) < 0)
>  			bad = _("not under version control");
> -		else if (lstat(dst, &st) == 0) {
> +		else if (lstat(dst, &st) == 0 &&
> +			 (!ignore_case || strcasecmp(src, dst))) {

Hmm, I would find it easier to read if it were:

		... if (lstat(dst, &st) == 0 &&
                	!(ignore_case && !strcasecmp(src, dst))) {

That is, "it is an error for dst to exist, unless we are on a case
insensitive filesystem and src and dst refer to the same file.", but
maybe it is just me.

More importantly, what is the end-user visible effect of this
change?  Is it fair to summarize it like this?

    On a case-insensitive filesystem, "mv hello.txt Hello.txt"
    always trigger the "dst already exists" error, because both
    names refer to the same file to MS-DOS, requiring the user to
    pass the "--force" option.  Allow it without "--force".

Overwriting an existing file with "mv hello.txt Hello.txt" on a case
sensitive filesystem *is* an unusual operation, and that is the
reason why we require "--force" to make sure that the user means it.
I have a slight suspicion that the same "mv hello.txt Hello.txt" on
a case insensitive filesystem, where two names are known (to the end
user of such a filesystem) to refer to the same path would equally
be a very unusual thing to do, and such an operation may deserve a
similar safety precaution to make sure that the user really meant to
do so by requiring "--force".

So, I dunno.

>  			bad = _("destination exists");
>  			if (force) {
>  				/*
> diff --git a/t/t6039-merge-ignorecase.sh b/t/t6039-merge-ignorecase.sh
> index dfc9f17..a977653 100755
> --- a/t/t6039-merge-ignorecase.sh
> +++ b/t/t6039-merge-ignorecase.sh
> @@ -35,7 +35,7 @@ test_expect_success 'merge with case-changing rename on both sides' '
>  	git reset --hard baseline &&
>  	git branch -D with-camel &&
>  	git checkout -b with-camel &&
> -	git mv --force TestCase testcase &&
> +	git mv TestCase testcase &&
>  	git commit -m "recase on branch" &&
>  	>foo &&
>  	git add foo &&