Issue #50: Make cd fully sh-compatible (cd -, ~ expansion, PWD/OLDPWD) in JS + Rust

[konard]

Issue #50: CWD with cd pattern

Fixes the directory-context problem from #50 where cd in one $\...`call did not affect later calls, and brings the built-incdto fullsh/bash parity so shell scripts translate directly to .mjs` and Rust.

Per maintainer feedback: "by default we use behavior similar to sh scripts,
so mjs and rust scripts can be easily translated from sh to mjs/rust by users."

What changed

cd now matches POSIX sh semantics in both the JavaScript and Rust
implementations (kept in lock-step for the language-parity check):

• cd with no argument changes to $HOME ($USERPROFILE fallback)
• cd ~ and cd ~/path tilde expansion
• cd - switches to $OLDPWD and prints the directory, like sh
  (errors with cd: OLDPWD not set when unset)
• a successful cd updates the PWD and OLDPWD environment variables
• relative targets resolve against the active cwd option
• the process directory persists across separate $ invocations (the original
  bug), while subshells ( ... ) still isolate and restore the cwd

Reproduction (before → after)

import { $ } from 'command-stream';
await $`cd /tmp`;
const { stdout } = await $`pwd`;
// before: original directory  →  after: /tmp

A runnable sh→mjs translation example lives in
js/examples/cd-cwd-sh-translation.mjs.

Tests

• js/tests/cwd-cd-pattern-issue.test.mjs — original-issue scenarios plus a new
  "sh-compatibility (drop-in translation from sh)" suite (cd→HOME, cd ~,
  cd ~/, cd -, PWD/OLDPWD, non-existent error, relative-to-cwd)
• js/tests/cd-virtual-command.test.mjs — strengthened cd - assertions
• rust/src/commands/cd.rs — 8 unit tests mirroring the JS behavior, serialized
  with an async mutex because cd mutates process-global cwd/env

All cd tests pass (JS: 37, Rust: 8). The only failing JS tests in this
environment are pre-existing jq-dependent suites (jq is not installed here),
unrelated to this change. Full Rust suite: 118 unit + integration tests pass,
cargo fmt --check and cargo clippy clean.

Docs & release

• js/README.md — new "Working Directory (cd and the cwd option)" section
  covering persistence, subshell isolation, cd vs. cwd, and the env-expansion
  limitation
• js/.changeset/cd-sh-compatibility.md — minor changeset
• rust/changelog.d/…_cd-sh-compatibility.md — minor changelog fragment

Fixes #50

[konard]

We need to double check everything. Make sure everything is documented, and by default we use behavior similar to sh scripts. So mjs and rust scripts can be easily translated from sh to mjs/rust by users.

[konard]

🤖 AI Work Session Started

Starting automated work session at 2026-06-10T09:54:41.361Z

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[konard]

Working session summary

All checks pass and the PR is clean and mergeable. The work for issue #50 is complete. Here's a summary of what was accomplished:

Summary

Issue #50 — cd did not maintain directory context between separate $\...`invocations, and the built-incddiverged from POSIXsh` semantics. Per maintainer feedback, the goal was full sh-parity in both the JS and Rust implementations so scripts translate directly.

Changes (PR #99, branch issue-50-02f42ae4)

Core fix — cd now matches sh/bash in both languages:

• js/src/commands/$.cd.mjs and rust/src/commands/cd.rs (kept in lock-step for the language-parity CI check):
  • cd (no arg) → $HOME ($USERPROFILE fallback)
  • cd ~ / cd ~/path tilde expansion
  • cd - → $OLDPWD and prints the directory (errors cd: OLDPWD not set when unset)
  • successful cd updates PWD/OLDPWD env vars
  • relative targets resolve against the cwd option
  • directory persists across separate $ calls (the original bug); subshells ( … ) still isolate/restore

Tests:

• js/tests/cwd-cd-pattern-issue.test.mjs — original-issue scenarios + new sh-compatibility suite (15 tests)
• js/tests/cd-virtual-command.test.mjs — strengthened cd - assertions
• rust/src/commands/cd.rs — 8 unit tests mirroring JS, serialized with an async mutex (global cwd/env mutation)
• Cross-platform fixes: normalized macOS /var→/private/var paths; skipped Unix-shell suites on Windows (matching repo convention in git-gh-cd.test.mjs)

Docs & release:

• js/README.md — new "Working Directory" section
• js/.changeset/cd-sh-compatibility.md (minor) and rust/changelog.d/…_cd-sh-compatibility.md (minor)
• js/examples/cd-cwd-sh-translation.mjs — runnable sh→mjs translation example

Verification

• All CI green across ubuntu/macOS/Windows for both JS (bun + node) and Rust, plus parity, changeset, and changelog-fragment checks.
• PR is MERGEABLE / CLEAN, marked ready for review, with main merged in.

PR: #99

The two CI hiccups along the way (a jq-not-installed local environment and a transient actions/cache failure on the Windows Rust job) were confirmed to be infrastructure-related, not code issues — the cache failure cleared on re-run.

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This summary was automatically extracted from the AI working session output.

[konard]

🤖 Solution Draft Log

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💰 Cost: $9.674513

📊 Context and tokens usage:

Claude Opus 4.8: (2 sub-sessions)

1. 116.8K / 1M (12%) input tokens, 45.9K / 128K (36%) output tokens
2. 113.1K / 1M (11%) input tokens, 32.4K / 128K (25%) output tokens

Total: (26.8K new + 206.9K cache writes + 12.3M cache reads) input tokens, 84.1K output tokens, $9.674513 cost

🤖 Models used:

• Tool: Anthropic Claude Code
• Requested: opus
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• View complete solution draft log

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Now working session is ended, feel free to review and add any feedback on the solution draft.

[konard]

🎉 Auto-merged

This pull request has been automatically merged by hive-mind.

• All CI checks have passed

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Auto-merged by hive-mind with --auto-merge flag