From 9c6cfc1ff0412b75592067e9017bf36a0e555078 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Sun, 10 Jul 2022 15:40:30 +0100
Subject: [PATCH] combine: throw error if duplicate directory name is specified

See: https://forum.rclone.org/t/v1-59-combine-qs/31814
---
 backend/combine/combine.go | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/backend/combine/combine.go b/backend/combine/combine.go
index 36fdc69c6..a65192647 100644
--- a/backend/combine/combine.go
+++ b/backend/combine/combine.go
@@ -206,9 +206,13 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (outFs fs
 				return err
 			}
 			mu.Lock()
-			f.upstreams[dir] = u
+			if _, found := f.upstreams[dir]; found {
+				err = fmt.Errorf("duplicate directory name %q", dir)
+			} else {
+				f.upstreams[dir] = u
+			}
 			mu.Unlock()
-			return nil
+			return err
 		})
 	}
 	err = g.Wait()