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orca/docs/reference/windows-setup-shell.md
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OrcaWinandOrcaWin ed7849eb7b fix(worktrees): stop silently switching existing Windows setup scripts to Git Bash (#12406)
* fix(worktrees): stop silently switching existing Windows setup scripts to Git Bash

#6967 derived the Windows setup-runner shell from `terminalWindowsShell`. On
upgrade, any Windows user whose terminal preference resolved to Git Bash had
their existing `orca.yaml` setup script (and issue command) handed to bash
instead of cmd.exe. Scripts authored against the cmd runner — `copy`, `xcopy`,
`set VAR=value`, `if errorlevel 1`, `%VAR%`, backslash paths — broke with no
migration and no warning, and the failure looked like Orca broke the project.

The conflation is also wrong in the steady state: a terminal preference is
per-user, so two people on the same repo got different interpreters for the
same orca.yaml and no project could write a setup script that worked for all
of its Windows contributors.

The interpreter is now a property of the script, declared the standard way:
a leading `#!` line. Native Windows keeps the historical `.cmd` runner unless
the script declares a POSIX shell, so no existing script changes behavior.
`resolveSetupRunnerShell` keeps its role as the feasibility gate — a bash
runner still requires the terminal to resolve to Git Bash, since the launch
command is typed into that shell and uses MSYS `/c/...` paths.

`buildWindowsRunnerScript` now drops a leading `#!` line rather than `call`ing
it, so a declared-bash script that falls back to cmd (Git Bash missing) fails
on a real setup line instead of aborting on errorlevel at line one.

WSL worktrees, POSIX platforms, and SSH hosts are untouched.

* fix(worktrees): keep the cmd setup runner launchable from a Git Bash pane

Adversarial review of this PR found that pinning the runner format per script
reopened issue #6896 one layer down.

- `WorktreeSetupLaunch.shell` had been redefined to mean "the format the runner
  file was written in". `resolveSetupRunnerCommand` consumes it as "the shell
  that types the launch command", so a Git Bash terminal with a batch setup
  script produced `cmd.exe /c "C:\...\setup-runner.cmd"` typed into a bash pane,
  where MSYS rewrites the `/c` switch into a drive path: cmd opens interactively
  and setup never runs. `shell` is the terminal's family again; the runner file's
  .cmd/.sh extension carries the format, and a batch runner launched from a POSIX
  pane reuses the existing PowerShell ProcessStartInfo launcher.
- The cmd runner dropped a leading `#!` line and ran the rest as batch, so a bash
  script reaching cmd (PowerShell/cmd terminal, or any SSH-to-Windows host) got
  its interpreter-agnostic prefix executed before failing mid-way. It now prints
  why and exits 1 without running anything.
- A `#!` line's option flags were discarded: `#!/usr/bin/env -S bash -euo
  pipefail` lost pipefail because the runner is launched as `bash <path>`. The
  generated posix runner now replays declared flags via `set` and drops the
  duplicate interpreter line.
- Docs cover the per-user setup command in repository hook settings, which goes
  through the same `#!` rule, and describe what the `#!` line does and does not
  select.

Tests: composed launch command for a POSIX pane + cmd runner (hooks, shared
runner command, setup sequencing gate, observed-setup signal), the cmd runner's
shebang refusal, and shebang flag replay. Each fails with the source reverted.

* fix(worktrees): replay only real `set` flags and keep the gate in the pane's shell

Two round-2 review findings:

- `#!/bin/bash -l` replayed `set -l`, which exits 2 and aborted the runner under
  its own `set -e` before a single setup line ran (all platforms). Only the flags
  `set` documents are replayed now; a bare `-o` with no option name is dropped
  instead of dumping the shell-option table.
- The wait-for-setup gate picked its language from the runner file, so a batch
  runner launched from a Git Bash pane got the PowerShell gate while the agent
  startup command was already POSIX-quoted — `Invoke-Expression` cannot parse
  `'\''`. The gate now follows the pane; the runner still launches through the
  ProcessStartInfo launcher, never through bash.

---------

Co-authored-by: OrcaWin <293788423+OrcaWin@users.noreply.github.com>
2026-08-03 23:25:50 -07:00

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Markdown

# Windows setup-runner shell
On native Windows, Orca writes the `orca.yaml` setup script (and the issue command) to a generated
runner file and types a launch command into a terminal. The runner is a **`.cmd` batch file by
default**, exactly as it has been since setup hooks shipped.
A script opts into bash by starting with a `#!` interpreter line:
```yaml
scripts:
setup: |
#!/usr/bin/env bash
[ -f .env ] || cp .env.example .env
pnpm install
```
Without that line the script keeps running under `cmd.exe`:
```yaml
scripts:
setup: |
copy .env.example .env
xcopy /E assets dist
```
## Why the script declares it, not the terminal preference
`terminalWindowsShell` says which shell *interactive terminals* open in. It says nothing about the
language a project's setup script is written in. Deriving the runner from it had two consequences:
- Windows users with batch-syntax setup scripts silently switched to bash on upgrade, so `copy`,
`xcopy`, `set VAR=value`, and `if errorlevel 1` stopped working.
- Two people on the same repo got different interpreters for the same `orca.yaml`, so no project
could write a setup script that worked for all of its Windows contributors.
A `#!` line is per-project, explicit, and identical for everyone who checks the repo out.
The same rule applies to the per-user setup command in **Settings → repository hooks**
(`repo.hookSettings.scripts.setup`): it is merged into the same script that reaches the runner, so a
POSIX one-liner stored there needs its own `#!` line to run under bash on Windows.
## What the `#!` line does and does not select
The generated runner is always executed by bash (`bash <runner>`; Git Bash on native Windows), on
every platform. The `#!` line therefore does two things:
- It declares the script is written for a POSIX shell, which is what selects the bash runner.
- Its option flags are replayed with `set`, so `#!/usr/bin/env -S bash -euo pipefail` really does
get `pipefail`. Without that replay the flags would be silently dropped, because `bash <runner>`
never parses the interpreter line. Only the flags `set` itself accepts
(`[--abefhkmnptuvxBCHP] [-o option]`) are replayed; invocation-only ones such as `-l` are
dropped, because `set -l` exits 2 and would abort the runner before its first line.
The interpreter name itself is not honored beyond "is this a POSIX shell": `#!/bin/sh` and
`#!/bin/zsh` scripts run under bash, exactly as they already did on macOS and Linux.
## Requirements for the bash runner
A `#!` line only takes effect when Orca can actually launch bash from the configured terminal — the
terminal shell must resolve to Git Bash (`resolveWindowsGitBashShellPath`). The generated runner
uses MSYS `/c/...` paths, which Cygwin and the WSL shim do not accept, and the launch command is
typed into whatever shell the terminal opened with.
When bash is not available (a PowerShell/cmd terminal, or an SSH-to-Windows host, which always uses
the remote's `.cmd` runner) the `#!` script is **not** executed under cmd. The generated `.cmd`
runner prints why and exits 1, because running the interpreter-agnostic prefix of a bash script
(`pnpm install`, `git submodule update`) and only failing at the first bash-only line leaves a
half-set-up worktree that looks finished.
## Launching a `.cmd` runner from a Git Bash terminal
The runner format and the shell that types the launch command are independent: a Git Bash terminal
with a batch-syntax setup script gets a `.cmd` runner launched from a bash pane. `cmd.exe /c
"C:\..."` cannot be used there — MSYS rewrites the bare `/c` switch into a drive path, so cmd opens
interactively and the runner never executes (issue #6896). Those launches reuse the PowerShell
`ProcessStartInfo` launcher (`buildWindowsCmdRunnerDelayedLaunchCommand`), which carries the switch
and the runner path outside the command line. `WorktreeSetupLaunch.shell` therefore describes the
launching pane; the runner file's `.cmd`/`.sh` extension describes the format.
The `wait-for-setup` gate follows the same split. The pane types the gate and already quoted the
agent startup command for itself, so a `.cmd` runner launched from a Git Bash pane still gets the
bash gate — PowerShell's `Invoke-Expression` cannot parse POSIX `'\''` escaping. The gate wraps the
same `ProcessStartInfo` launcher, so the batch runner is never handed to bash.
WSL worktrees and non-Windows platforms are unaffected: they always use the bash runner. SSH hosts
choose their runner from the remote path format, never from local Windows preferences.