[PATCH] reset: avoid reflog update on no-op reset

[Pushkar Singh <pushkarkumarsingh1970@gmail.com>]

When "git reset" is invoked with a target that already matches HEAD,
it currently writes a reflog entry even though no reference is updated.

Detect this no-op case and avoid updating ORIG_HEAD and HEAD, skipping
the reflog entry entirely.

Add a regression test to ensure no reflog entry is written for a no-op
reset.

Signed-off-by: Pushkar Singh <pushkarkumarsingh1970@gmail.com>
---
 builtin/reset.c   |  4 ++++
 t/t1410-reflog.sh | 15 +++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/builtin/reset.c b/builtin/reset.c
index ed35802af1..900c2f2fe8 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -309,6 +309,10 @@ static int reset_refs(const char *rev, const struct object_id *oid)
 		old_orig = &oid_old_orig;
 	if (!repo_get_oid(the_repository, "HEAD", &oid_orig)) {
 		orig = &oid_orig;
+		if (oideq(orig, oid)) {
+			strbuf_release(&msg);
+			return 0;
+		}
 		set_reflog_message(&msg, "updating ORIG_HEAD", NULL);
 		refs_update_ref(get_main_ref_store(the_repository), msg.buf,
 				"ORIG_HEAD", orig, old_orig, 0,
diff --git a/t/t1410-reflog.sh b/t/t1410-reflog.sh
index ce71f9a30a..54f8692c53 100755
--- a/t/t1410-reflog.sh
+++ b/t/t1410-reflog.sh
@@ -533,6 +533,21 @@ test_expect_success 'reflog for symref with unborn target can be listed' '
 	)
 '
 
+test_expect_success 'reset does not write reflog entry on no-op' '
+	git init no-op-reset &&
+	(
+		cd no-op-reset &&
+		echo a >file &&
+		git add file &&
+		git commit -m initial &&
+
+		before=$(git reflog | wc -l) &&
+		git reset HEAD &&
+		after=$(git reflog | wc -l) &&
+		test "$before" = "$after"
+	)
+'
+
 test_expect_success 'reflog with invalid object ID can be listed' '
 	test_when_finished "rm -rf repo" &&
 	git init repo &&
-- 
2.43.0