Re: [RFC PATCH v2 1/4] Prevent diff machinery from examining assume-unchanged entries on worktree

> diff --git a/diff-lib.c b/diff-lib.c
> index b7813af..f5787f6 100644
> --- a/diff-lib.c
> +++ b/diff-lib.c
> @@ -337,6 +337,8 @@ static void do_oneway_diff(struct unpack_trees_options *o,
>  	struct rev_info *revs = o->unpack_data;
>  	int match_missing, cached;
>  
> +	/* if the entry is not checked out, don't examine work tree */
> +	cached = o->index_only || (idx && (idx->ce_flags & CE_VALID));
>  	/*
>  	 * Backward compatibility wart - "diff-index -m" does
>  	 * not mean "do not ignore merges", but "match_missing".
> @@ -344,7 +346,6 @@ static void do_oneway_diff(struct unpack_trees_options *o,
>  	 * But with the revision flag parsing, that's found in
>  	 * "!revs->ignore_merges".
>  	 */
> -	cached = o->index_only;
>  	match_missing = !revs->ignore_merges;
>  
>  	if (cached && idx && ce_stage(idx)) {

> diff --git a/t/t4039-diff-assume-unchanged.sh b/t/t4039-diff-assume-unchanged.sh
> new file mode 100755
> index 0000000..d0e46a7
> --- /dev/null
> +++ b/t/t4039-diff-assume-unchanged.sh
> @@ -0,0 +1,31 @@
> +#!/bin/sh
> +
> +test_description='diff with assume-unchanged entries'
> +
> +. ./test-lib.sh
> +
> +# external diff has been tested in t4020-diff-external.sh
> +
> +test_expect_success 'setup' '
> +	echo zero > zero &&
> +	git add zero &&
> +	git commit -m zero &&
> +	echo one > one &&
> +	echo two > two &&
> +	git add one two &&
> +	git commit -m onetwo &&
> +	git update-index --assume-unchanged one &&
> +	echo borked >> one &&
> +	test "$(git ls-files -v one)" = "h one"
> +'

> +
> +test_expect_success 'diff-index does not examine assume-unchanged entries' '
> +	git diff-index HEAD^ -- one | grep -q 5626abf0f72e58d7a153368ba57db4c673c0e171 
> +'
> +
> +# TODO ced_uptodate()

> +test_expect_success 'diff-files does not examine assume-unchanged entries' '
> +	/usr/bin/git diff-files -- one
> +'
> +
> +test_done