[PATCH v2 1/4] diff: ignore --ita-[in]visible-in-index when diffing worktree-to-tree

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

This option is supposed to fix the diff of "diff-files" (not reporting
ita entries as new files) and "diff-index --cached <tree>" ( showing
ita entries as present in the index with empty content) but not
"diff-index <tree>".

When --ita-invisible-in-index is set on "git diff-index <tree>",
unpack_trees() will eventually call oneway_diff() on the ita entry
with the same code flow as "diff-index --cached <tree>". We want to
ignore the ita entry for "diff-index --cached <tree>" but not
"diff-index <tree>" since the latter will examine and produce a diff
based on worktree entry's (real) content, not ita index entry's
(empty) content.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 diff-lib.c            | 8 ++++++--
 t/t2203-add-intent.sh | 2 +-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/diff-lib.c b/diff-lib.c
index 104f954a25..a9f38eb5a3 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -389,8 +389,12 @@ static void do_oneway_diff(struct unpack_trees_options *o,
 	struct rev_info *revs = o->unpack_data;
 	int match_missing, cached;
 
-	/* i-t-a entries do not actually exist in the index */
-	if (revs->diffopt.ita_invisible_in_index &&
+	/*
+	 * i-t-a entries do not actually exist in the index (if we're
+	 * looking at its content)
+	 */
+	if (o->index_only &&
+	    revs->diffopt.ita_invisible_in_index &&
 	    idx && ce_intent_to_add(idx)) {
 		idx = NULL;
 		if (!tree)
diff --git a/t/t2203-add-intent.sh b/t/t2203-add-intent.sh
index 78236dc7d8..3ab07cb404 100755
--- a/t/t2203-add-intent.sh
+++ b/t/t2203-add-intent.sh
@@ -70,7 +70,7 @@ test_expect_success 'i-t-a entry is simply ignored' '
 	git commit -m second &&
 	test $(git ls-tree HEAD -- nitfol | wc -l) = 0 &&
 	test $(git diff --name-only HEAD -- nitfol | wc -l) = 1 &&
-	test $(git diff --name-only --ita-invisible-in-index HEAD -- nitfol | wc -l) = 0 &&
+	test $(git diff --name-only --ita-invisible-in-index HEAD -- nitfol | wc -l) = 1 &&
 	test $(git diff --name-only --ita-invisible-in-index -- nitfol | wc -l) = 1
 '
 
-- 
2.17.0.705.g3525833791