[question] Is there a way to skip licenseHeader for legacy files while keeping other formatters active?

**Environment:**

- Java
- Spotless Maven Plugin

**Background**
Our project contains both new and legacy Java files:

- **New files** contain only the new license header:
```java
// New License Header
```
- **Legacy files** contain multiple historical license headers, for example:
```java
// New License Header

// Old License Header
```

**Problem**
When configuring Spotless with:

```xml

${project.basedir}/tools/spotless/license-header.txt
package |import |module

```

Spotless replaces **all** license headers in **all files**, including legacy files that should keep their original headers.

This causes two issues:

1. Legacy files lose their historical license information
2. If I exclude legacy files from `licenseHeader`, then other formatters (`googleJavaFormat`, `eclipse`, `prettier`, `idea`, `tableTestFormatter`, `importOrder`) will also stop applying to them

**Expected Behavior**
- New files should receive the new license header
- Legacy files should **keep their existing headers**, but still be formatted by other Spotless steps

**Question**
Is there a recommended way to configure Spotless so that:

- `licenseHeader` applies **only to new files**
- Other formatters still apply to **all files**
- Legacy files are not modified by the license step

Issue に示されている Maven Spotless の設定と licenseHeader の区切り文字から始め、一覧にあるフォーマット手順が Java ファイルにどのように適用されるかを確認します。ほかの手順を除外せずに licenseHeader を新規ファイルに限定できるかを判断します。新規ファイルに header が付与され、既存の header が変更されず、ほかのすべての formatter が引き続き実行されれば完了です。

索引モデルが issue の本文から書いたものです。