fix(install): Windows installs under a long profile path no longer fail "Clone succeeded, but checkout failed"

install.ps1 clones into %LOCALAPPDATA%\hermes\.hermes-clone-<pid>-<random>\tree
before publishing, which puts the deepest tracked file (a 159-character zh-Hans
docs path) past MAX_PATH once LOCALAPPDATA is longer than ~55 characters. Git
for Windows then refuses the file ("Filename too long"), every clone attempt
and the deferred checkout fail the same way, and the user sees "fatal: unable to
checkout working tree" from both the PowerShell one-liner and Hermes-Setup.

Clone with --config core.longpaths=true so the setting lands before the first
checkout and stays in the repo for `hermes update`; an installer rerun over an
existing checkout sets it too.

Salvages the long-path half of #72744 by @Imagineer99, written against the
pre-rewrite installer.

Co-authored-by: Lee Jackson <samleejackson0@gmail.com>

scripts/install.ps1

@@ -870,6 +870,8 @@ function Stage-Repository {
     }
     if (Test-Path (Join-Path $InstallDir ".git")) {
         Log "Updating $InstallDir ($Branch)"
+        # A checkout cloned before longpaths was set: a deep path past MAX_PATH fails checkout.
+        Invoke-Native { git -C $InstallDir config core.longpaths true } | Out-Null
         # An explicit HERMES_REPO_URL names the source for reruns too, not
         # just the first clone.
         if ($env:HERMES_REPO_URL) {
@@ -989,6 +991,10 @@ function Stage-Repository {
         # branch tip first fetches and rewrites every file the two differ in.
         $checkout = @()
         if ($Commit) { $checkout = @('--no-checkout') }
+        # Staging dir + deepest tracked path (~160) pass MAX_PATH (260) once LOCALAPPDATA
+        # is longer than ~55 characters (a ~33-character user name), and checkout dies with
+        # "Filename too long". --config lands before checkout and stays for `hermes update`.
+        $longPaths = @('--config', 'core.longpaths=true')
         try {
             $cloned = $false
             $deferred = $false
@@ -1000,7 +1006,7 @@ function Stage-Repository {
                 # checkout and history walk (#129712).
                 $cloneLabel = "Cloning $RepoUrl ($Branch) into $InstallDir"
                 if ($attempt -gt 1) { $cloneLabel += " (attempt $attempt of 3)" }
-                Invoke-Logged $cloneLabel { git clone @progress --filter=blob:none @checkout --branch $Branch $RepoUrl $tree }
+                Invoke-Logged $cloneLabel { git clone @progress @longPaths --filter=blob:none @checkout --branch $Branch $RepoUrl $tree }
                 if (-not $LASTEXITCODE) { $cloned = $true; break }
                 Remove-Item -LiteralPath $tree -Recurse -Force -ErrorAction SilentlyContinue
                 if ($attempt -lt 3) { Start-Sleep -Seconds ($attempt * 5) }
@@ -1009,7 +1015,7 @@ function Stage-Repository {
                 # The checkout step is where throttled downloads die: clone the
                 # graph alone, then retry materializing the tree separately.
                 Write-Warn "direct clone failed; trying deferred checkout"
-                Invoke-Logged "Cloning history" { git clone @progress --filter=blob:none --no-checkout --branch $Branch $RepoUrl $tree }
+                Invoke-Logged "Cloning history" { git clone @progress @longPaths --filter=blob:none --no-checkout --branch $Branch $RepoUrl $tree }
                 if (-not $LASTEXITCODE) { $cloned = $true; $deferred = $true }
             }
             if (-not $cloned) { Fail "git clone failed; no checkout published$(Get-NativeDetail)" git_clone_failed }

tests/scripts/install/test_install_clone_throttle_fallback.py

@@ -66,9 +66,10 @@ def _run_repository_stage(installer: str, tmp_path: Path, install: Path, origin_
         # pwsh on POSIX cannot run the Windows-only pinned Git: seed its PM store slot with host git.
         version = json.loads((ROOT / "pm" / "lock.json").read_text(encoding="utf-8-sig"))["packages"]["git"]["version"]
         cmd = tmp_path / "tools" / f"git-{version}-win32-x64" / "cmd"
-        cmd.mkdir(parents=True)
+        cmd.mkdir(parents=True, exist_ok=True)
         for name in ("git.exe", "git"):
-            (cmd / name).symlink_to(shutil.which("git"))
+            if not (cmd / name).exists():
+                (cmd / name).symlink_to(shutil.which("git"))
         env.update(HERMES_RUNTIME_DIR=str(tmp_path / "tools"), PATH=str(cmd) + os.pathsep + env["PATH"])
     return subprocess.run([POWERSHELL, "-NoProfile", "-File", str(ROOT / "scripts" / "install.ps1"),
                            "-Stage", "repository", "-NonInteractive", "-InstallDir", str(install),
@@ -130,3 +131,31 @@ def test_clone_failure_reason_carries_gits_own_error(tmp_path, installer):
     assert result.returncode != 0
     assert "git clone failed; no checkout published: fatal:" in output, output
     assert "no-such-repo.git" in output.split("no checkout published: fatal:", 1)[1].splitlines()[0]
+
+
+@pytest.mark.live_system_guard_bypass
+@pytest.mark.skipif(POWERSHELL is None, reason="needs PowerShell")
+def test_ps1_checkout_keeps_long_paths_enabled(tmp_path):
+    """Windows checkouts sit past MAX_PATH under a long profile root: git must be told to allow it."""
+    origin = tmp_path / "origin.git"
+    source = tmp_path / "source"
+    install = tmp_path / "install"
+    subprocess.run(["git", "init", "--bare", "-b", "main", str(origin)], check=True, capture_output=True)
+    def git(cwd, *args):
+        return subprocess.run(["git", "-C", str(cwd), *args], check=False,
+                              capture_output=True, text=True, encoding="utf-8", errors="replace")
+    source.mkdir()
+    for args in (("init", "-b", "main"), ("config", "user.email", "fixture@example.invalid"),
+                 ("config", "user.name", "Fixture"), ("commit", "--allow-empty", "-m", "fixture"),
+                 ("push", origin.as_posix(), "main")):
+        assert git(source, *args).returncode == 0
+    git(origin, "config", "uploadpack.allowFilter", "true")
+
+    fresh = _run_repository_stage("ps1", tmp_path, install, origin.as_uri())
+    assert fresh.returncode == 0, fresh.stdout + fresh.stderr
+    assert git(install, "config", "--local", "--get", "core.longpaths").stdout.strip() == "true"
+
+    git(install, "config", "--local", "--unset", "core.longpaths")  # a checkout from an older installer
+    rerun = _run_repository_stage("ps1", tmp_path, install, origin.as_uri())
+    assert rerun.returncode == 0, rerun.stdout + rerun.stderr
+    assert git(install, "config", "--local", "--get", "core.longpaths").stdout.strip() == "true"