diff --git a/wt-status.c b/wt-status.c
index e12adb26b9..95942399f8 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -612,6 +612,30 @@ static void wt_status_collect_updated_cb(struct diff_queue_struct *q,
 	}
 }
 
+void wt_status_collect_changes_trees(struct wt_status *s,
+				     const struct object_id *old_treeish,
+				     const struct object_id *new_treeish)
+{
+	struct diff_options opts = { 0 };
+
+	repo_diff_setup(s->repo, &opts);
+	opts.output_format = DIFF_FORMAT_CALLBACK;
+	opts.format_callback = wt_status_collect_updated_cb;
+	opts.format_callback_data = s;
+	opts.detect_rename = s->detect_rename >= 0 ? s->detect_rename : opts.detect_rename;
+	opts.rename_limit = s->rename_limit >= 0 ? s->rename_limit : opts.rename_limit;
+	opts.rename_score = s->rename_score >= 0 ? s->rename_score : opts.rename_score;
+	opts.flags.recursive = 1;
+	diff_setup_done(&opts);
+
+	diff_tree_oid(old_treeish, new_treeish, "", &opts);
+	diffcore_std(&opts);
+	diff_flush(&opts);
+	wt_status_get_state(s->repo, &s->state, 0);
+
+	diff_free(&opts);
+}
+
 static void wt_status_collect_changes_worktree(struct wt_status *s)
 {
 	struct rev_info rev;
diff --git a/wt-status.h b/wt-status.h
index e40a27214a..e9fe32e98c 100644
--- a/wt-status.h
+++ b/wt-status.h
@@ -153,6 +153,15 @@ void wt_status_add_cut_line(struct wt_status *s);
 void wt_status_prepare(struct repository *r, struct wt_status *s);
 void wt_status_print(struct wt_status *s);
 void wt_status_collect(struct wt_status *s);
+
+/*
+ * Collect all changes between the two trees. Changes will be displayed as if
+ * they were staged into the index.
+ */
+void wt_status_collect_changes_trees(struct wt_status *s,
+				     const struct object_id *old_treeish,
+				     const struct object_id *new_treeish);
+
 /*
  * Frees the buffers allocated by wt_status_collect.
  */