fix(s3): use path.Dir instead of filepath.Dir in directoryDiff (#4950)

registry/storage/driver/s3-aws/s3.go

@@ -21,7 +21,7 @@ import (
 	"math"
 	"net/http"
 	"net/url"
-	"path/filepath"
+	"path"
 	"slices"
 	"sort"
 	"strconv"
@@ -1230,6 +1230,11 @@ func (d *driver) doWalk(parentCtx context.Context, objectCount *int64, from, sta
 //
 //	directoryDiff("/", "/path/to/folder/folder/file")
 //	// => [ "/path", "/path/to", "/path/to/folder", "/path/to/folder/folder" ]
+//
+// prev and current are S3 object keys, which always use "/" as a separator
+// regardless of host OS, so this must use path.Dir rather than filepath.Dir:
+// on Windows, filepath.Dir converges to "\" instead of "/", so the loop's
+// "/" exit condition never fires and it never terminates.
 func directoryDiff(prev, current string) []string {
 	var paths []string
 
@@ -1239,7 +1244,7 @@ func directoryDiff(prev, current string) []string {
 
 	parent := current
 	for {
-		parent = filepath.Dir(parent)
+		parent = path.Dir(parent)
 		if parent == "/" || parent == prev || strings.HasPrefix(prev+"/", parent+"/") {
 			break
 		}

registry/storage/driver/s3-aws/s3_test.go

@@ -341,6 +341,55 @@ func TestIsSubpath(t *testing.T) {
 	}
 }
 
+func TestDirectoryDiff(t *testing.T) {
+	tests := []struct {
+		name     string
+		prev     string
+		current  string
+		expected []string
+	}{
+		{
+			name:     "immediate child",
+			prev:     "/path/to/folder",
+			current:  "/path/to/folder/folder/file",
+			expected: []string{"/path/to/folder/folder"},
+		},
+		{
+			name:     "sibling folder",
+			prev:     "/path/to/folder/folder1",
+			current:  "/path/to/folder/folder2/file",
+			expected: []string{"/path/to/folder/folder2"},
+		},
+		{
+			name:     "sibling folder, prev is a file",
+			prev:     "/path/to/folder/folder1/file",
+			current:  "/path/to/folder/folder2/file",
+			expected: []string{"/path/to/folder/folder2"},
+		},
+		{
+			name:     "multiple missing directories",
+			prev:     "/path/to/folder/folder1/file",
+			current:  "/path/to/folder/folder2/folder1/file",
+			expected: []string{"/path/to/folder/folder2", "/path/to/folder/folder2/folder1"},
+		},
+		{
+			name:     "from root, deeply nested",
+			prev:     "/",
+			current:  "/path/to/folder/folder/file",
+			expected: []string{"/path", "/path/to", "/path/to/folder", "/path/to/folder/folder"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			actual := directoryDiff(tt.prev, tt.current)
+			if !slices.Equal(actual, tt.expected) {
+				t.Fatalf("directoryDiff(%q, %q) = %v, want %v", tt.prev, tt.current, actual, tt.expected)
+			}
+		})
+	}
+}
+
 func TestEmptyRootList(t *testing.T) {
 	skipCheck(t)