[PATCH v3 1/4] apply: read in the index in --intent-to-add mode

From: Raymond E. Pasco <ray@ameretat.dev>
Date: Jul 7, 2025, 12:12 UTC
Message-ID: <20250707121534.2933349-2-ray@ameretat.dev>
In-Reply-To: <20250707121534.2933349-1-ray@ameretat.dev>

There are three main modes of operation for apply: applying only to the worktree, applying to the worktree and index (--index), and applying only to the index (--cached).

The --intent-to-add flag modifies the first of these modes, applying only to the worktree, in a way which touches the index, because intents to add are special index entries. However, since its introduction in cff5dc09ed (apply: add --intent-to-add, 2018-05-26), it has not worked correctly in any but the most trivial (empty repository) cases, because the index is never read in (in apply, this is done in read_apply_cache()) before writing to it.

This causes the operation to clobber the old, correct index with a new empty-tree index before writing intent-to-add entries to this empty index; the final result is that the index now records every existing file in the repository as deleted, which is incorrect.

This error can be corrected by first reading the index. The update_index flag is correctly set if ita_only is true, because this flag causes the index to be updated. However, if we merely gate the call to read_apply_cache() behind update_index, then it will not be read when state->apply is false, even if it must be checked due to being in --index or --cached mode. Therefore, we instead read the index if it will be either checked or updated, because reading the index is a prerequisite to either.

Reported-by: Ryan Hodges <rhodges@cisco.com>
Original-patch-by: Johannes Altmanninger <aclopte@gmail.com>
Signed-off-by: Raymond E. Pasco <ray@ameretat.dev>
---
 apply.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/apply.c b/apply.c
index 8bbe6ed224..c8d4517c0a 100644
--- a/apply.c
+++ b/apply.c
@@ -4833,7 +4833,7 @@ static int apply_patch(struct apply_state *state,
 					       LOCK_DIE_ON_ERROR);
 	}
 
-	if (state->check_index && read_apply_cache(state) < 0) {
+	if ((state->check_index || state->update_index) && read_apply_cache(state) < 0) {
 		error(_("unable to read index file"));
 		res = -128;
 		goto end;

-- 
2.50.0.229.gc167f4d905