feat(i18n): compose pairing records during merges

scripts/install-lefthook.mjs

@@ -27,6 +27,13 @@ const INSTALL_LOCK_INITIALIZATION_TIMEOUT_MS = 1_000
 const INSTALL_LOCK_POLL_MS = 50
 const ALLOW_HOOKS_PATH_OVERRIDE = 'DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE'
 const REPOSITORY_EXTENSION_PATTERN = '^extensions\\.'
+const PAIRING_MERGE_DRIVER_CONFIG = [
+  ['merge.dsh-translation-pairing.name', 'DeepSeek Harness bilingual pairing records'],
+  [
+    'merge.dsh-translation-pairing.driver',
+    'node --import tsx/esm scripts/merge-translation-pairing.ts %O %A %B %P',
+  ],
+]
 
 function errorCode(error) {
   return typeof error === 'object' && error !== null && 'code' in error
@@ -595,6 +602,82 @@ function refuseScopedHooksPath(entry) {
   )
 }
 
+function installPairingMergeDriver(root, worktreeConfigPath) {
+  const added = []
+  try {
+    for (const [key, expected] of PAIRING_MERGE_DRIVER_CONFIG) {
+      const entries = includedFileConfigEntries(root, worktreeConfigPath, key)
+      const includedEntry = entries.find(entry => !originIsFile(entry.origin, root, worktreeConfigPath))
+      if (includedEntry !== undefined) {
+        throw new Error(
+          `refusing pairing merge-driver config from an included worktree file (${configSource(includedEntry)})`,
+        )
+      }
+      const existing = assertSingle(entries.map(entry => entry.value), `worktree ${key}`)
+      const effectiveBefore = effectiveConfigEntry(root, key)
+      if (effectiveBefore?.scope === 'command') {
+        throw new Error(
+          `refusing command-scoped ${key} (${configSource(effectiveBefore)}); `
+          + 'transient configuration cannot be replaced by the worktree installer',
+        )
+      }
+      if (existing === undefined && effectiveBefore !== undefined && effectiveBefore.value !== expected) {
+        throw new Error(
+          `refusing to mask inherited ${key} (${configSource(effectiveBefore)}); `
+          + 'remove or integrate the custom pairing merge driver explicitly',
+        )
+      }
+      if (existing !== undefined && existing !== expected) {
+        throw new Error(
+          `refusing to replace worktree ${key} value ${JSON.stringify(existing)}; `
+          + 'remove or integrate the custom pairing merge driver explicitly',
+        )
+      }
+      if (existing === undefined) {
+        git(['config', '--worktree', key, expected], root)
+        added.push(key)
+      }
+      const installed = includedFileConfigEntries(root, worktreeConfigPath, key)
+      if (
+        installed.length !== 1
+        || installed[0]?.value !== expected
+        || !originIsFile(installed[0].origin, root, worktreeConfigPath)
+      ) {
+        throw new Error(`new worktree-local ${key} did not become the direct worktree value`)
+      }
+      const effectiveAfter = effectiveConfigEntry(root, key)
+      if (
+        effectiveAfter === undefined
+        || effectiveAfter.scope !== 'worktree'
+        || effectiveAfter.value !== expected
+        || !originIsFile(effectiveAfter.origin, root, worktreeConfigPath)
+      ) {
+        throw new Error(`new worktree-local ${key} did not become the effective direct worktree value`)
+      }
+    }
+  } catch (error) {
+    const rollbackErrors = []
+    for (const key of added.reverse()) {
+      try {
+        git(['config', '--worktree', '--unset-all', key], root)
+      } catch (rollbackError) {
+        rollbackErrors.push(rollbackError)
+      }
+    }
+    if (rollbackErrors.length > 0) {
+      throw new AggregateError(
+        [error, ...rollbackErrors],
+        `Pairing merge-driver configuration failed: ${String(error)}; `
+        + `rollback also failed: ${rollbackErrors.map(String).join('; ')}`,
+      )
+    }
+    throw error
+  }
+  return () => {
+    for (const key of added.reverse()) git(['config', '--worktree', '--unset-all', key], root)
+  }
+}
+
 async function main() {
   if (process.env.CI === 'true' || process.env.GITHUB_ACTIONS === 'true') return
   if (typeof lefthookPackage.bin?.lefthook !== 'string') return
@@ -682,7 +765,9 @@ async function main() {
     applyWorktreeConfigMigration(root, commonConfigPath, migration)
 
     let pathChanged = false
+    let rollbackPairingMergeDriver = () => {}
     try {
+      rollbackPairingMergeDriver = installPairingMergeDriver(root, worktreeConfigPath)
       git(['config', '--worktree', 'core.hooksPath', hooksPath], root)
       pathChanged = worktreePath !== hooksPath
       const installedEntry = effectiveConfigEntry(root, 'core.hooksPath')
@@ -697,6 +782,7 @@ async function main() {
       runLefthook(root, lefthook)
       updateOwnershipMarker(ownedHooksDirectory.markerPath, hooksPath)
     } catch (error) {
+      const rollbackErrors = []
       if (pathChanged) {
         try {
           if (worktreePath === undefined) {
@@ -705,13 +791,21 @@ async function main() {
             git(['config', '--worktree', 'core.hooksPath', worktreePath], root)
           }
         } catch (rollbackError) {
-          throw new AggregateError(
-            [error, rollbackError],
-            `Lefthook installation failed: ${String(error)}; `
-            + `worktree hook rollback also failed: ${String(rollbackError)}`,
-          )
+          rollbackErrors.push(rollbackError)
         }
       }
+      try {
+        rollbackPairingMergeDriver()
+      } catch (rollbackError) {
+        rollbackErrors.push(rollbackError)
+      }
+      if (rollbackErrors.length > 0) {
+        throw new AggregateError(
+          [error, ...rollbackErrors],
+          `Lefthook installation failed: ${String(error)}; `
+          + `worktree integration rollback also failed: ${rollbackErrors.map(String).join('; ')}`,
+        )
+      }
       throw error
     }
   } catch (error) {