fix(git): enable Windows long paths for worktree creation (local, sparse, and SSH hosts) (#15866)

Co-authored-by: hwantage <hwantagexsw2@gmail.com>

src/shared/windows-long-path-git-args.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, it } from 'vitest'
+
+import { windowsLongPathGitArgs } from './windows-long-path-git-args'
+
+describe('windowsLongPathGitArgs', () => {
+  it('enables long paths for a Windows drive path', () => {
+    expect(windowsLongPathGitArgs('C:\\Users\\dev\\repo', 'win32')).toEqual([
+      '-c',
+      'core.longpaths=true'
+    ])
+  })
+
+  it.each(['darwin', 'linux'] as const)('returns nothing on %s', (platform) => {
+    expect(windowsLongPathGitArgs('/home/dev/repo', platform)).toEqual([])
+  })
+
+  it.each(['\\\\wsl.localhost\\Ubuntu\\home\\dev\\repo', '\\\\wsl$\\Ubuntu\\home\\dev\\repo'])(
+    'returns nothing for the WSL UNC path %s',
+    (cwd) => {
+      expect(windowsLongPathGitArgs(cwd, 'win32')).toEqual([])
+    }
+  )
+
+  it('never mutates the shared constant', () => {
+    const first = windowsLongPathGitArgs('C:\\repo', 'win32')
+    first.push('--bogus')
+    expect(windowsLongPathGitArgs('C:\\repo', 'win32')).toEqual(['-c', 'core.longpaths=true'])
+  })
+})

src/shared/windows-long-path-git-args.ts

@@ -0,0 +1,25 @@
+import { parseWslUncPath } from './wsl-paths'
+
+const WINDOWS_LONG_PATH_GIT_ARGS = ['-c', 'core.longpaths=true'] as const
+
+/**
+ * Global `git -c` options that let a Windows checkout exceed MAX_PATH.
+ *
+ * Why command scope: Git for Windows aborts deep checkouts with "Filename too
+ * long" unless core.longpaths is on, and `-c` applies it to this invocation
+ * only — never `--global`, `--system`, or `--local`, so no user config is
+ * written. Available since Git 1.9, well under the 2.25 baseline.
+ *
+ * Why keyed off cwd rather than a wslDistro option: a `C:\...` cwd can still be
+ * served by host git.exe even when a distro is configured, and Linux git parses
+ * and ignores the key, so only a true `\\wsl.localhost\...` path opts out.
+ */
+export function windowsLongPathGitArgs(
+  cwd: string,
+  platform: NodeJS.Platform = process.platform
+): string[] {
+  if (platform !== 'win32' || parseWslUncPath(cwd)) {
+    return []
+  }
+  return [...WINDOWS_LONG_PATH_GIT_ARGS]
+}