feat(fnos-mount-manager): 添加受管区块差异输出功能

当检查发现受管区块与本地预览不匹配时，现在会统一输出差异对比，
方便用户直接查看本地预览和目标受管区块之间的具体差别。

新增了 fm_report_managed_block_diff 函数来处理差异显示逻辑，
该函数会创建临时文件并使用 diff 命令比较预期区块和实际区块，
然后将差异内容以标准化格式输出到错误流中。

同时为 check 命令添加了相应的测试用例，验证差异输出功能的正确性。

Author: mudssky

linux/fnos/fnos-mount-manager/commands/check.sh

@@ -5,6 +5,44 @@ if [[ -n "${FNOS_MOUNT_MANAGER_CHECK_LOADED:-}" ]]; then
 fi
 FNOS_MOUNT_MANAGER_CHECK_LOADED=1
 
+# 在受管区块不一致时输出统一 diff，方便直接看 preview 和目标文件的差异。
+fm_report_managed_block_diff() {
+  local expected_block="$1"
+  local actual_block="$2"
+  local expected_file
+  local actual_file
+  expected_file="$(mktemp)"
+  actual_file="$(mktemp)"
+
+  printf '%s\n' "${expected_block}" > "${expected_file}"
+  printf '%s\n' "${actual_block}" > "${actual_file}"
+
+  if command -v diff >/dev/null 2>&1; then
+    local diff_output
+    diff_output="$(
+      diff -u \
+        --label "local-preview" \
+        --label "target-managed-block" \
+        "${expected_file}" \
+        "${actual_file}" || true
+    )"
+    if [[ -n "${diff_output}" ]]; then
+      fm_log "error" "Managed block diff:"
+      while IFS= read -r line; do
+        printf '[fnos-mount-manager][error] %s\n' "${line}" >&2
+      done <<< "${diff_output}"
+    fi
+  else
+    fm_log "error" "Managed block diff: diff command not available"
+    fm_log "error" "Expected block:"
+    printf '%s\n' "${expected_block}" >&2
+    fm_log "error" "Actual block:"
+    printf '%s\n' "${actual_block}" >&2
+  fi
+
+  rm -f "${expected_file}" "${actual_file}"
+}
+
 # 检查单个渲染产物是否与当前配置匹配，并把异常累加到错误计数里。
 fm_check_rendered_file() {
   local config_path="$1"
@@ -119,6 +157,7 @@ EOF
 
       if [[ "${expected_block}" != "${actual_block}" ]]; then
         fm_log "error" "Managed block in ${target} does not match the local preview"
+        fm_report_managed_block_diff "${expected_block}" "${actual_block}"
         error_count=$(( error_count + 1 ))
       fi
     else

linux/fnos/fnos-mount-manager/fnos-mount-manager.sh

@@ -627,6 +627,44 @@ if [[ -n "${FNOS_MOUNT_MANAGER_CHECK_LOADED:-}" ]]; then
 fi
 FNOS_MOUNT_MANAGER_CHECK_LOADED=1
 
+# 在受管区块不一致时输出统一 diff，方便直接看 preview 和目标文件的差异。
+fm_report_managed_block_diff() {
+  local expected_block="$1"
+  local actual_block="$2"
+  local expected_file
+  local actual_file
+  expected_file="$(mktemp)"
+  actual_file="$(mktemp)"
+
+  printf '%s\n' "${expected_block}" > "${expected_file}"
+  printf '%s\n' "${actual_block}" > "${actual_file}"
+
+  if command -v diff >/dev/null 2>&1; then
+    local diff_output
+    diff_output="$(
+      diff -u \
+        --label "local-preview" \
+        --label "target-managed-block" \
+        "${expected_file}" \
+        "${actual_file}" || true
+    )"
+    if [[ -n "${diff_output}" ]]; then
+      fm_log "error" "Managed block diff:"
+      while IFS= read -r line; do
+        printf '[fnos-mount-manager][error] %s\n' "${line}" >&2
+      done <<< "${diff_output}"
+    fi
+  else
+    fm_log "error" "Managed block diff: diff command not available"
+    fm_log "error" "Expected block:"
+    printf '%s\n' "${expected_block}" >&2
+    fm_log "error" "Actual block:"
+    printf '%s\n' "${actual_block}" >&2
+  fi
+
+  rm -f "${expected_file}" "${actual_file}"
+}
+
 # 检查单个渲染产物是否与当前配置匹配，并把异常累加到错误计数里。
 fm_check_rendered_file() {
   local config_path="$1"
@@ -741,6 +779,7 @@ EOF
 
       if [[ "${expected_block}" != "${actual_block}" ]]; then
         fm_log "error" "Managed block in ${target} does not match the local preview"
+        fm_report_managed_block_diff "${expected_block}" "${actual_block}"
         error_count=$(( error_count + 1 ))
       fi
     else

linux/fnos/fnos-mount-manager/tests/check.test.ts

@@ -1,3 +1,4 @@
+import fs from 'node:fs'
 import { afterEach, describe, expect, it } from 'vitest'
 import {
   cleanupWorkspace,
@@ -111,4 +112,37 @@ describe('fnos mount manager check', () => {
       '# BEGIN FNOS MOUNT MANAGER',
     )
   })
+
+  it('prints a managed block diff when the target block drifts from the local preview', () => {
+    const workspace = createWorkspace()
+    workspaces.push(workspace)
+
+    installCheckSystemctl(workspace)
+    ensureFakeDevice(workspace, 'LABEL:local-book')
+    ensureFakeDevice(workspace, 'UUID:local-debut')
+    expect(runSource(workspace, ['generate']).exitCode).toBe(0)
+    expect(
+      runSource(workspace, ['apply', '--target', workspace.targetFstab])
+        .exitCode,
+    ).toBe(0)
+
+    const drifted = readText(workspace.targetFstab).replace(
+      'UUID=local-debut /mnt/local/debutDisk ntfs nofail,uid=1000,gid=1000,umask=022,big_writes,x-systemd.device-timeout=45 0 0',
+      'UUID=local-debut /mnt/local/debutDisk ntfs nofail,uid=1000,gid=1000,umask=022 0 0',
+    )
+    fs.writeFileSync(workspace.targetFstab, drifted, 'utf8')
+
+    const result = runSource(workspace, [
+      'check',
+      '--target',
+      workspace.targetFstab,
+    ])
+
+    expect(result.exitCode).not.toBe(0)
+    expect(result.stderr + result.stdout).toContain('Managed block diff:')
+    expect(result.stderr + result.stdout).toContain('--- local-preview')
+    expect(result.stderr + result.stdout).toContain('+++ target-managed-block')
+    expect(result.stderr + result.stdout).toContain('-UUID=local-debut /mnt/local/debutDisk ntfs nofail,uid=1000,gid=1000,umask=022,big_writes,x-systemd.device-timeout=45 0 0')
+    expect(result.stderr + result.stdout).toContain('+UUID=local-debut /mnt/local/debutDisk ntfs nofail,uid=1000,gid=1000,umask=022 0 0')
+  })
 })