Always copy source directory contents, not the directory itself

internal/syncengine/rsync_runner.go

@@ -69,15 +69,28 @@ func (r *RsyncRunner) buildArgs(pair *SyncPairConfig) []string {
 		args = append(args, "--delete")
 	}
 
+	src := ensureDirSlash(pair.Source)
 	if pair.Direction == "pull" {
-		args = append(args, pair.Dest, pair.Source)
+		args = append(args, pair.Dest, src)
 	} else {
-		args = append(args, pair.Source, pair.Dest)
+		args = append(args, src, pair.Dest)
 	}
 
 	return args
 }
 
+// ensureDirSlash guarantees the source path is treated by rsync as a
+// directory whose contents are copied, regardless of whether the user
+// supplied a trailing slash. This avoids the common foot-gun where
+// "rsync host:/path/series /dest/" creates /dest/series/<contents> nested
+// inside an extra "series" subdirectory.
+func ensureDirSlash(p string) string {
+	if strings.HasSuffix(p, "/") {
+		return p
+	}
+	return p + "/"
+}
+
 type MachineKeys struct {
 	Host    string
 	Port    int