Leverage GIT_UNUSED macro to explicitly mark a function parameter as purposely unused

tests-clar/diff/diff_helpers.c

@@ -27,7 +27,9 @@ int diff_file_fn(
 	float progress)
 {
 	diff_expects *e = cb_data;
-	(void)progress;
+
+	GIT_UNUSED(progress);
+
 	e->files++;
 	switch (delta->status) {
 	case GIT_DELTA_ADDED: e->file_adds++; break;
@@ -48,9 +50,11 @@ int diff_hunk_fn(
 	size_t header_len)
 {
 	diff_expects *e = cb_data;
-	(void)delta;
-	(void)header;
-	(void)header_len;
+
+	GIT_UNUSED(delta);
+	GIT_UNUSED(header);
+	GIT_UNUSED(header_len);
+
 	e->hunks++;
 	e->hunk_old_lines += range->old_lines;
 	e->hunk_new_lines += range->new_lines;
@@ -66,10 +70,12 @@ int diff_line_fn(
 	size_t content_len)
 {
 	diff_expects *e = cb_data;
-	(void)delta;
-	(void)range;
-	(void)content;
-	(void)content_len;
+
+	GIT_UNUSED(delta);
+	GIT_UNUSED(range);
+	GIT_UNUSED(content);
+	GIT_UNUSED(content_len);
+
 	e->lines++;
 	switch (line_origin) {
 	case GIT_DIFF_LINE_CONTEXT: