Re: [PATCH] merge-recursive.c: Fix case-changing merge bug

[Junio C Hamano <gitster@pobox.com>]

David Turner <dturner@twopensource.com> writes:

> On a case-insensitive filesystem, when merging, a file would be
> wrongly deleted from the working tree if an incoming commit had
> renamed it changing only its case.  When merging a rename, the file
> with the old name would be deleted -- but since the filesystem
> considers the old name to be the same as the new name, the new
> file would in fact be deleted.
>
> We avoid this by not deleting files that have a case-clone in the
> index at stage 0.
>
> Signed-off-by: David Turner <dturner@twitter.com>
> ---
>  merge-recursive.c           |  6 ++++++
>  t/t7063-merge-ignorecase.sh | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 38 insertions(+)
>  create mode 100755 t/t7063-merge-ignorecase.sh
>
> diff --git a/merge-recursive.c b/merge-recursive.c
> index 4177092..cab16fa 100644
> --- a/merge-recursive.c
> +++ b/merge-recursive.c
> @@ -589,6 +589,12 @@ static int remove_file(struct merge_options *o, int clean,
>  			return -1;
>  	}
>  	if (update_working_directory) {
> +		if (ignore_case) {
> +			struct cache_entry *ce;
> +			ce = cache_file_exists(path, strlen(path), ignore_case);
> +			if (ce && ce_stage(ce) == 0)
> +				return 0;
> +		}
>  		if (remove_path(path))
>  			return -1;
>  	}

Thanks.

I wonder what happens if you did the same merge using the resolve
strategy, though.  If you see a similar issue, and the true reason
of the breakage turns out to be because three-way merge performed by
unpack_trees() (with opts.update set to 1) considers that these
paths that only differ in case in "our" tree, in the index and in
the working tree are different paths (I am not saying that is the
case, but that was one of my first hunches after seeing the initial
report) then it may suggest that the above might not be the best
change to fix the issue.

> diff --git a/t/t7063-merge-ignorecase.sh b/t/t7063-merge-ignorecase.sh
> new file mode 100755
> index 0000000..6d4959f
> --- /dev/null
> +++ b/t/t7063-merge-ignorecase.sh

Hmmm, did you really have to add a file dedicated for this single
test?

> @@ -0,0 +1,32 @@
> +#!/bin/sh
> +
> +test_description='git-merge with case-changing rename on case-insensitive file system'
> +
> +. ./test-lib.sh
> +
> +if ! test_have_prereq CASE_INSENSITIVE_FS
> +then
> +	skip_all='skipping case insensitive tests - case sensitive file system'
> +	test_done
> +fi
> +
> +test_expect_success 'merge with case-changing rename with ignorecase=true' '
> +	test $(git config core.ignorecase) = true &&
> +	touch TestCase &&
> +	git add TestCase &&
> +	git commit -m "add TestCase" &&
> +	git checkout -b with-camel &&
> +	touch foo &&
> +	git add foo &&
> +	git commit -m "intervening commit" &&
> +	git checkout master &&
> +	git rm TestCase &&
> +	touch testcase &&
> +	git add testcase &&
> +	git commit -m "rename to testcase" &&
> +	git checkout with-camel &&
> +	git merge master -m "merge" &&
> +	test -e testcase
> +'
> +
> +test_done