perf: preserve user Git checkout worker settings

docs/reference/git-compatibility.md

@@ -53,17 +53,6 @@ in one record and pick at parse time.
 | --------------- | ----------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------- |
 | `%(decorate:…)` | Git 2.43 separates commit decorations with `\x1f`, so ref names containing commas survive | The same record also carries `%D` (Git 2.10); an unexpanded `%(decorate` placeholder selects it, at the cost of comma-splitting |
 
-### Parallel checkout configuration
-
-Native macOS worktree creation and prepared-checkout materialization pass the
-command-local setting `-c checkout.workers=4`. Parallel checkout arrived in Git
-2.32; Git 2.25–2.31 accepts and ignores this unknown configuration key, preserving
-serial checkout without a rejected command or retry. No capability-cache entry is
-needed for this setting. The real-binary contract checks the worker boundary using
-Trace2 and verifies checked-out content and clean status. Windows, WSL, Linux, and
-SSH keep their existing checkout settings pending host measurements. The setting
-is never persisted to repository or user configuration.
-
 ## Why Not `simple-git`
 
 `simple-git` is a process wrapper around the installed Git binary. Its custom

src/main/git/add-sparse-worktree.test.ts

@@ -167,7 +167,7 @@ branch refs/heads/main
     const calls = getGitCalls()
     expect(calls).toEqual(
       expect.arrayContaining([
-        'git -c checkout.workers=4 worktree add --no-checkout --no-track -b feature/test /repo-feature',
+        'git worktree add --no-checkout --no-track -b feature/test /repo-feature',
         'git config --get push.autoSetupRemote',
         'git config --local push.autoSetupRemote true',
         'git sparse-checkout init --cone',

src/main/git/worktree-add-creation-config.test.ts

@@ -68,8 +68,6 @@ describe('addWorktree', () => {
       [['rev-parse', '--verify', '--quiet', 'refs/remotes/origin/main^{commit}'], { cwd: '/repo' }],
       [
         [
-          '-c',
-          'checkout.workers=4',
           'worktree',
           'add',
           '--no-track',
@@ -104,7 +102,7 @@ describe('addWorktree', () => {
 
     expect(gitExecFileAsyncMock.mock.calls).toEqual([
       [
-        ['-c', 'checkout.workers=4', 'worktree', 'add', '/repo-feature', 'feature/test'],
+        ['worktree', 'add', '/repo-feature', 'feature/test'],
         { cwd: '/repo', timeout: WORKTREE_ADD_TIMEOUT_MS }
       ]
     ])
@@ -184,13 +182,7 @@ describe('addWorktree', () => {
       })
 
       expect(gitExecFileAsyncMock).toHaveBeenCalledWith(
-        [
-          ...(platform === 'darwin' ? ['-c', 'checkout.workers=4'] : []),
-          'worktree',
-          'add',
-          '/repo-feature',
-          'feature/test'
-        ],
+        ['worktree', 'add', '/repo-feature', 'feature/test'],
         { cwd: '/repo', timeout: WORKTREE_ADD_TIMEOUT_MS }
       )
     }
@@ -235,16 +227,7 @@ describe('addWorktree', () => {
 
     expect(gitExecFileAsyncMock.mock.calls).toEqual([
       [
-        [
-          '-c',
-          'checkout.workers=4',
-          'worktree',
-          'add',
-          '--no-track',
-          '-b',
-          'feature/no-base',
-          '/repo-feature'
-        ],
+        ['worktree', 'add', '--no-track', '-b', 'feature/no-base', '/repo-feature'],
         { cwd: '/repo', timeout: WORKTREE_ADD_TIMEOUT_MS }
       ],
       [['config', '--get', 'push.autoSetupRemote'], { cwd: '/repo-feature' }]
@@ -319,8 +302,6 @@ describe('addWorktree', () => {
       [['rev-parse', '--verify', '--quiet', 'refs/remotes/origin/main^{commit}'], { cwd: '/repo' }],
       [
         [
-          '-c',
-          'checkout.workers=4',
           'worktree',
           'add',
           '--no-track',
@@ -359,8 +340,6 @@ describe('addWorktree', () => {
       [['rev-parse', '--verify', '--quiet', 'refs/remotes/origin/main^{commit}'], { cwd: '/repo' }],
       [
         [
-          '-c',
-          'checkout.workers=4',
           'worktree',
           'add',
           '--no-track',
@@ -400,8 +379,6 @@ describe('addWorktree', () => {
       [['rev-parse', '--verify', '--quiet', 'refs/remotes/origin/main^{commit}'], { cwd: '/repo' }],
       [
         [
-          '-c',
-          'checkout.workers=4',
           'worktree',
           'add',
           '--no-track',
@@ -442,8 +419,6 @@ describe('addWorktree', () => {
       [['rev-parse', '--verify', '--quiet', 'refs/remotes/origin/main^{commit}'], { cwd: '/repo' }],
       [
         [
-          '-c',
-          'checkout.workers=4',
           'worktree',
           'add',
           '--no-track',
@@ -475,8 +450,6 @@ describe('addWorktree', () => {
     ])
     expect(gitExecFileAsyncMock.mock.calls[1]).toEqual([
       [
-        '-c',
-        'checkout.workers=4',
         'worktree',
         'add',
         '--no-track',
@@ -503,8 +476,6 @@ describe('addWorktree', () => {
       ['rev-parse', '--verify', '--quiet', 'refs/remotes/release/main^{commit}'],
       ['rev-parse', '--verify', '--quiet', 'refs/heads/release/main^{commit}'],
       [
-        '-c',
-        'checkout.workers=4',
         'worktree',
         'add',
         '--no-track',
@@ -546,8 +517,6 @@ describe('addWorktree', () => {
       ['rev-parse', '--verify', '--quiet', 'refs/remotes/release/main^{commit}'],
       ['rev-parse', '--verify', '--quiet', 'refs/heads/release/main^{commit}'],
       [
-        '-c',
-        'checkout.workers=4',
         'worktree',
         'add',
         '--no-track',

src/main/git/worktree-add-local-base-refresh.test.ts

@@ -82,7 +82,6 @@ describe('addWorktree', () => {
       [['reset', '--hard', 'remote-main'], { cwd: '/repo' }],
       [
         [
-          ...(process.platform === 'darwin' ? ['-c', 'checkout.workers=4'] : []),
           'worktree',
           'add',
           '--no-track',
@@ -320,7 +319,6 @@ describe('addWorktree', () => {
       'refs/remotes/origin/main^{commit}'
     ])
     expect(gitExecFileAsyncMock.mock.calls[7]?.[0]).toEqual([
-      ...(process.platform === 'darwin' ? ['-c', 'checkout.workers=4'] : []),
       'worktree',
       'add',
       '--no-track',
@@ -380,7 +378,6 @@ describe('addWorktree', () => {
       ],
       [
         [
-          ...(process.platform === 'darwin' ? ['-c', 'checkout.workers=4'] : []),
           'worktree',
           'add',
           '--no-track',
@@ -437,7 +434,6 @@ describe('addWorktree', () => {
 
     expect(result.localBaseRefRefresh).toBeUndefined()
     expect(gitExecFileAsyncMock.mock.calls.map((call) => call[0])).toContainEqual([
-      ...(process.platform === 'darwin' ? ['-c', 'checkout.workers=4'] : []),
       'worktree',
       'add',
       '--no-track',
@@ -559,7 +555,6 @@ describe('addWorktree', () => {
       ],
       [
         [
-          ...(process.platform === 'darwin' ? ['-c', 'checkout.workers=4'] : []),
           'worktree',
           'add',
           '--no-track',

src/main/git/worktree-add-local-base-suggestion.test.ts

@@ -95,7 +95,6 @@ describe('addWorktree', () => {
       ['rev-parse', '--verify', '--quiet', 'refs/remotes/origin/main^{commit}'],
       ['rev-list', '--left-right', '--count', 'refs/heads/main...refs/remotes/origin/main'],
       [
-        ...(process.platform === 'darwin' ? ['-c', 'checkout.workers=4'] : []),
         'worktree',
         'add',
         '--no-track',

src/main/git/worktree-add.ts

@@ -20,7 +20,6 @@ import type {
 } from './worktree-operation-options'
 import { gitExecOptions, resolveWorktreeAddTimeoutMs } from './worktree-operation-options'
 import { bumpWorktreeScanGeneration } from './worktree-scan-cache'
-import { worktreeCheckoutGitArgs } from '../../shared/worktree-checkout-config'
 
 export type WorktreeAddBaseContext = AddWorktreeResult & {
   effectiveBase: string
@@ -188,12 +187,7 @@ async function performAddWorktree(
   let localBaseRefRefresh: LocalBaseRefRefreshResult | undefined
   let localBaseRefUpdateSuggestion: LocalBaseRefUpdateSuggestion | undefined
   // Why: enable long paths for this Windows checkout without changing user Git config.
-  const args = [
-    ...windowsLongPathGitArgs(repoPath),
-    ...worktreeCheckoutGitArgs(options),
-    'worktree',
-    'add'
-  ]
+  const args = [...windowsLongPathGitArgs(repoPath), 'worktree', 'add']
   let effectiveBase: string | undefined
   if (noCheckout) {
     args.push('--no-checkout')

src/main/git/worktree-create-preparation.ts

@@ -14,7 +14,6 @@ import { withRepoRefMaintenancePaused } from './local-repo-ref-maintenance'
 import { gitExecFileAsync } from './runner'
 import { runWithGitReadCacheInvalidation } from './status'
 import { invalidateWslLinkedWorktreeGitRouting } from './wsl-linked-worktree-git-routing'
-import { worktreeCheckoutGitArgs } from '../../shared/worktree-checkout-config'
 
 function gitExecOptions(
   cwd: string,
@@ -93,13 +92,7 @@ export async function prepareWorktreeCreateCheckout(
           invalidateWslLinkedWorktreeGitRouting(worktreePath)
           // Why: reset materializes files without running user post-checkout hooks before submit.
           await gitExecFileAsync(
-            [
-              ...windowsLongPathGitArgs(worktreePath),
-              ...worktreeCheckoutGitArgs(options),
-              'reset',
-              '--hard',
-              effectiveBase
-            ],
+            [...windowsLongPathGitArgs(worktreePath), 'reset', '--hard', effectiveBase],
             { ...gitExecOptions(worktreePath, options), timeout: resolveWorktreeAddTimeoutMs() }
           )
           await gitExecFileAsync(
@@ -236,13 +229,7 @@ export async function finalizePreparedWorktree(
       const preparedHeadOutput = preparedResult.value.stdout
       if (preparedHeadOutput.trim() !== targetHead) {
         await gitExecFileAsync(
-          [
-            ...windowsLongPathGitArgs(preparedPath),
-            ...worktreeCheckoutGitArgs(options),
-            'reset',
-            '--hard',
-            targetHead
-          ],
+          [...windowsLongPathGitArgs(preparedPath), 'reset', '--hard', targetHead],
           gitExecOptions(preparedPath, finalizeGitOptions)
         )
       }

src/shared/git-binary-compatibility.test.ts

@@ -23,7 +23,6 @@ import {
   gitlabMergeRequestHeadLocalRef,
   reviewHeadRemoteRefComponent
 } from './review-head-tracking-ref'
-import { worktreeCheckoutGitArgs } from './worktree-checkout-config'
 
 const execFileAsync = promisify(execFile)
 const image = process.env.ORCA_GIT_COMPAT_IMAGE
@@ -112,48 +111,6 @@ describeBinaryCompatibility('real Git binary compatibility', () => {
     }
   })
 
-  it('materializes parallel checkouts with a serial fallback before Git 2.32', async () => {
-    await runGit(['worktree', 'add', '--detach', 'parallel-source', 'HEAD'])
-    await Promise.all(
-      Array.from({ length: 16 }, (_, i) =>
-        writeFile(join(repoPath, 'parallel-source', `parallel-${i}.txt`), `file ${i}\n`)
-      )
-    )
-    await runGit(['-C', 'parallel-source', 'add', '.'])
-    await runGit(['-C', 'parallel-source', 'commit', '-qm', 'parallel fixture'])
-    const head = (await runGit(['-C', 'parallel-source', 'rev-parse', 'HEAD'])).stdout.trim()
-    await runGit(['worktree', 'add', '--detach', '--no-checkout', 'parallel-wt', head])
-    try {
-      const result = await runGit(
-        [
-          '-C',
-          'parallel-wt',
-          ...worktreeCheckoutGitArgs({}, 'darwin'),
-          '-c',
-          'checkout.thresholdForParallelism=0',
-          'reset',
-          '--hard',
-          'HEAD'
-        ],
-        { GIT_TRACE2_EVENT: '1' }
-      )
-      expect(result.stderr.includes('checkout--worker')).toBe(supports(2, 32))
-      expect(
-        (await readFile(join(repoPath, 'parallel-wt', 'tracked.txt'), 'utf8')).replaceAll(
-          '\r\n',
-          '\n'
-        )
-      ).toBe('compatibility\n')
-      expect((await runGit(['-C', 'parallel-wt', 'status', '--porcelain'])).stdout).toBe('')
-      await expect(
-        runGit(['config', '--local', '--get', 'checkout.workers'])
-      ).rejects.toMatchObject({ code: 1 })
-    } finally {
-      await runGit(['worktree', 'remove', '--force', 'parallel-wt'])
-      await runGit(['worktree', 'remove', '--force', 'parallel-source'])
-    }
-  })
-
   it('quietly distinguishes present and absent branch refs', async () => {
     const head = (await runGit(['rev-parse', 'HEAD'])).stdout.trim()
     await runGit(['branch', 'quiet-probe-present', head])

src/shared/worktree-checkout-config.test.ts

@@ -1,12 +0,0 @@
-import { describe, expect, it } from 'vitest'
-import { worktreeCheckoutGitArgs } from './worktree-checkout-config'
-
-describe('worktree checkout concurrency', () => {
-  it('bounds native Mac checkout workers without changing other execution hosts', () => {
-    expect(worktreeCheckoutGitArgs({}, 'darwin')).toEqual(['-c', 'checkout.workers=4'])
-    expect(worktreeCheckoutGitArgs({ wslDistro: 'Ubuntu' }, 'darwin')).toEqual([])
-    expect(worktreeCheckoutGitArgs({}, 'win32')).toEqual([])
-    expect(worktreeCheckoutGitArgs({ wslDistro: 'Ubuntu' }, 'win32')).toEqual([])
-    expect(worktreeCheckoutGitArgs({}, 'linux')).toEqual([])
-  })
-})

src/shared/worktree-checkout-config.ts

@@ -1,7 +0,0 @@
-export function worktreeCheckoutGitArgs(
-  options: { wslDistro?: string } = {},
-  platform: NodeJS.Platform = process.platform
-): string[] {
-  // Four workers halved native Mac checkout time; Git before 2.32 ignores this config.
-  return platform === 'darwin' && !options.wslDistro ? ['-c', 'checkout.workers=4'] : []
-}