订阅列表可以调顺序

每行末尾两个箭头，鼠标划过那一行才显现。proxy-providers 是映射，顺序只
影响界面呈现，内核不看；交换的是两个用户订阅在映射里的位置，中间夹着的
链式副本留在原地——它们不在列表上，跟着挪只会把 diff 撑大。

顺序写在配置文件里，所以走保存链路，不是运行时动作。

shared/providers.test.ts

@@ -5,6 +5,7 @@ import {
   addFileSubscription,
   addSubscription,
   listSubscriptions,
+  moveSubscription,
   providerNames,
   removeSubscription,
   renameSubscription,
@@ -280,6 +281,48 @@ describe('删除前的引用检查', () => {
   })
 })
 
+describe('调整订阅顺序', () => {
+  /** 三个用户订阅，外加一份接在中间的订阅副本。 */
+  function three(): ConfigObject {
+    let data: ConfigObject = {}
+    for (const name of ['A', 'B', 'C']) data = addSubscription(data, name, `https://${name}.example`)
+    return data
+  }
+
+  it('上移和下移交换相邻两个订阅', () => {
+    expect(listSubscriptions(moveSubscription(three(), 'B', -1)).map((s) => s.name)).toEqual([
+      'B',
+      'A',
+      'C',
+    ])
+    expect(listSubscriptions(moveSubscription(three(), 'B', 1)).map((s) => s.name)).toEqual([
+      'A',
+      'C',
+      'B',
+    ])
+  })
+
+  it('到头了原样返回，配置对象不变', () => {
+    const data = three()
+    expect(moveSubscription(data, 'A', -1)).toBe(data)
+    expect(moveSubscription(data, 'C', 1)).toBe(data)
+    expect(moveSubscription(data, '不存在', 1)).toBe(data)
+  })
+
+  it('夹在中间的订阅副本留在原地', () => {
+    const withCopy = applySetup(
+      { ...three(), listeners: [{ name: 'test1', type: 'mixed', port: 7778 }] },
+      'test1',
+      { proxy: { sources: ['B'], filter: null }, chain: { sources: ['B'], filter: null } },
+    )
+    const copy = chainProviderName('test1', 'B')
+    const before = Object.keys(withCopy['proxy-providers'] as ConfigObject).indexOf(copy)
+    const after = moveSubscription(withCopy, 'A', 1)
+    expect(listSubscriptions(after).map((s) => s.name)).toEqual(['B', 'A', 'C'])
+    expect(Object.keys(after['proxy-providers'] as ConfigObject).indexOf(copy)).toBe(before)
+  })
+})
+
 describe('缓存路径撞名', () => {
   it('名字只差符号时净化成同一个路径，能认出来', () => {
     const data = addSubscription({}, '订阅 A', 'https://a.example/sub')