feat: 更新扩展命令以支持大小写变体的处理和测试

tests/integration/extension_flow_test.go

@@ -76,3 +76,50 @@ func TestExtensionCommandFlow(t *testing.T) {
 		t.Fatalf("expected poster.JPG after undo: %v", err)
 	}
 }
+
+func TestExtensionCommandSkipsCaseVariantsWithoutSource(t *testing.T) {
+	t.Parallel()
+
+	tmp := t.TempDir()
+	createFile(t, filepath.Join(tmp, "image.jpeg"))
+	createFile(t, filepath.Join(tmp, "poster.JPG"))
+	createFile(t, filepath.Join(tmp, "logo.jpg"))
+
+	var previewOut bytes.Buffer
+	preview := renamercmd.NewRootCommand()
+	preview.SetOut(&previewOut)
+	preview.SetErr(&previewOut)
+	preview.SetArgs([]string{"extension", ".jpeg", ".jpg", "--dry-run", "--path", tmp})
+
+	if err := preview.Execute(); err != nil {
+		t.Fatalf("preview command failed: %v\noutput: %s", err, previewOut.String())
+	}
+
+	output := previewOut.String()
+	if !strings.Contains(output, "image.jpeg -> image.jpg") {
+		t.Fatalf("expected preview output to include image rename, got:\n%s", output)
+	}
+	if strings.Contains(output, "poster.JPG -> poster.jpg") {
+		t.Fatalf("expected poster.JPG to be excluded from preview, got:\n%s", output)
+	}
+
+	var applyOut bytes.Buffer
+	apply := renamercmd.NewRootCommand()
+	apply.SetOut(&applyOut)
+	apply.SetErr(&applyOut)
+	apply.SetArgs([]string{"extension", ".jpeg", ".jpg", "--yes", "--path", tmp})
+
+	if err := apply.Execute(); err != nil {
+		t.Fatalf("apply command failed: %v\noutput: %s", err, applyOut.String())
+	}
+
+	if _, err := os.Stat(filepath.Join(tmp, "image.jpg")); err != nil {
+		t.Fatalf("expected image.jpg after apply: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(tmp, "poster.JPG")); err != nil {
+		t.Fatalf("expected poster.JPG to remain uppercase: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(tmp, "poster.jpg")); !os.IsNotExist(err) {
+		t.Fatalf("expected poster.jpg not to exist, err=%v", err)
+	}
+}