[PATCH v2 1/3] fsmonitor: skip lstat deletion check during git diff-index

["Nipunn Koorapati via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Nipunn Koorapati <nipunn@xxxxxxxxxxx>

Teach git to honor fsmonitor rather than issuing an lstat
when checking for dirty local deletes. Eliminates O(files)
lstats during `git diff HEAD`

Signed-off-by: Nipunn Koorapati <nipunn@xxxxxxxxxxx>
---
 diff-lib.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/diff-lib.c b/diff-lib.c
index b73cc1859a49..3fb538ad18e9 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -30,7 +30,7 @@
  */
 static int check_removed(const struct cache_entry *ce, struct stat *st)
 {
-	if (lstat(ce->name, st) < 0) {
+	if (!(ce->ce_flags & CE_FSMONITOR_VALID) && lstat(ce->name, st) < 0) {
 		if (!is_missing_file_error(errno))
 			return -1;
 		return 1;
@@ -574,6 +574,7 @@ int run_diff_index(struct rev_info *revs, unsigned int option)
 	struct object_id oid;
 	const char *name;
 	char merge_base_hex[GIT_MAX_HEXSZ + 1];
+	struct index_state *istate = revs->diffopt.repo->index;
 
 	if (revs->pending.nr != 1)
 		BUG("run_diff_index must be passed exactly one tree");
@@ -581,6 +582,8 @@ int run_diff_index(struct rev_info *revs, unsigned int option)
 	trace_performance_enter();
 	ent = revs->pending.objects;
 
+	refresh_fsmonitor(istate);
+
 	if (merge_base) {
 		diff_get_merge_base(revs, &oid);
 		name = oid_to_hex_r(merge_base_hex, &oid);
-- 
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