v0.2.4: stop export loop on Ctrl+C instead of flooding failures

- Add IsCancelled() to Bridge interface
- Check bridge.IsCancelled() before each export in serial/parallel/backupTree
- Parallel workers mark remaining slots as 'cancelled' instead of exporting
- Add photos_request_is_cancelled to ObjC and C stub

cmd/photoscli/main.go

@@ -263,6 +263,9 @@ func backupTree(nodes []photos.CollectionNode, outDir string, targetSize int, or
 	total := 0
 	failed := 0
 	for _, node := range nodes {
+		if bridge.IsCancelled() {
+			break
+		}
 		path := outDir + "/" + sanitizePathComponent(node.Name)
 		if node.Kind == "folder" {
 			n, t, f, err := backupTree(node.Children, path, targetSize, originals, stderr, bridge)
@@ -306,6 +309,9 @@ func exportAssetsSerial(assets []photos.Asset, outDir string, targetSize int, or
 	exported := 0
 	failed := 0
 	for i, a := range assets {
+		if bridge.IsCancelled() {
+			break
+		}
 		result, exportErr := exportOne(bridge, a, outDir, targetSize, originals, i)
 		progressBar(stderr, exported+failed+1, total, dirPrefix+result.Filename, result.Size, result.Cloud)
 		if exportErr != nil {
@@ -337,6 +343,11 @@ func exportAssetsParallel(assets []photos.Asset, outDir string, targetSize int,
 		go func() {
 			defer wg.Done()
 			for i := range jobs {
+				if bridge.IsCancelled() {
+					slots[i].err = fmt.Errorf("cancelled")
+					close(slots[i].done)
+					continue
+				}
 				result, exportErr := exportOne(bridge, assets[i], outDir, targetSize, originals, i)
 				slots[i].result = result
 				slots[i].err = exportErr

cmd/photoscli/main_test.go

@@ -50,6 +50,7 @@ func (m *mockBridge) ExportOriginal(assetID, out string, index int) (photos.Expo
 	return photos.ExportResult{Filename: "test.jpg", Size: 2048, Cloud: "cloud"}, nil
 }
 func (m *mockBridge) Cancel() { m.cancelled = true }
+func (m *mockBridge) IsCancelled() bool { return m.cancelled }
 
 func runWith(args []string, b photos.Bridge) (string, string, int) {
 	var out, err bytes.Buffer