[meta] Add comprehensive .github/copilot-instructions.md for better AI code assistance

This comprehensive guide helps GitHub Copilot better understand and navigate the nvm codebase by providing:

- Complete architecture explanation of nvm's POSIX-compliant design across multiple shells
- Detailed mapping of top-level commands to internal functions (install, use, ls, alias, etc.)
- Comprehensive testing infrastructure guide using urchin framework
- Shell environment setup for bash, zsh, dash, sh, and ksh
- CI environment details for GitHub Actions and Travis CI
- shellcheck setup and usage guidelines
- Development best practices for POSIX compliance and multi-shell compatibility
- Windows support via WSL2, Cygwin, and Git Bash
- Complete internal function categorization and debugging techniques

The documentation covers all aspects of the codebase to enable more accurate AI assistance when working with nvm's complex shell script architecture.

.github/copilot-instructions.md

@@ -0,0 +1,427 @@
+# nvm Copilot Instructions
+
+This document provides guidance for GitHub Copilot when working with the Node Version Manager (nvm) codebase.
+
+## Overview
+
+nvm is a version manager for Node.js, implemented as a POSIX-compliant function that works across multiple shells (sh, dash, bash, ksh, zsh). The codebase is primarily written in shell script and emphasizes portability and compatibility.
+
+### Core Architecture
+
+- **Main script**: `nvm.sh` - Contains all core functionality and the main `nvm()` function
+- **Installation script**: `install.sh` - Handles downloading and installing nvm itself
+- **Execution wrapper**: `nvm-exec` - Allows running commands with specific Node.js versions
+- **Bash completion**: `bash_completion` - Provides tab completion for bash users
+- **Tests**: Comprehensive test suite in `test/` directory using the [urchin](https://www.npmjs.com/package/urchin) test framework
+
+## Key Files and Their Purposes
+
+### `nvm.sh`
+The core functionality file containing:
+- Main `nvm()` function (starts around line 3000)
+- All internal helper functions (prefixed with `nvm_`)
+- Command implementations for install, use, ls, etc.
+- Shell compatibility logic
+- POSIX compliance utilities
+
+### `install.sh`
+Handles nvm installation via curl/wget/git:
+- Downloads nvm from GitHub
+- Sets up directory structure
+- Configures shell integration
+- Supports both git clone and script download methods
+
+### `nvm-exec`
+Simple wrapper script that:
+- Sources nvm.sh with `--no-use` flag
+- Switches to specified Node version via `NODE_VERSION` env var or `.nvmrc`
+- Executes the provided command with that Node version
+
+## Top-Level nvm Commands and Internal Functions
+
+### Core Commands
+
+#### `nvm install [version]`
+- **Internal functions**: `nvm_install_binary()`, `nvm_install_source()`, `nvm_download_artifact()`
+- Downloads and installs specified Node.js version
+- Automatically `nvm use`s that version after installation
+- Supports LTS versions, version ranges, and built-in aliases (like `node`, `stable`) and user-defined aliases
+- Can install from binary or compile from source
+- When compiling from source, accepts additional arguments that are passed to the compilation task
+
+#### `nvm use [version]`
+- **Internal functions**: `nvm_resolve_alias()`, `nvm_version_path()`, `nvm_change_path()`
+- Switches current shell to use specified Node.js version
+- Updates PATH environment variable
+- Supports `.nvmrc` file integration
+
+#### `nvm ls [pattern]`
+- **Internal functions**: `nvm_ls()`, `nvm_tree_contains_path()`
+- Lists installed Node.js versions
+- Supports pattern matching and filtering
+- Shows current version and aliases
+
+#### `nvm ls-remote [pattern]`
+- **Internal functions**: `nvm_ls_remote()`, `nvm_download()`, `nvm_ls_remote_index_tab()`
+- Lists available Node.js versions from nodejs.org and iojs.org, or the env-var-configured mirrors
+- Supports LTS filtering and pattern matching
+- Downloads version index on-demand
+
+#### `nvm alias [name] [version]`
+- **Internal functions**: `nvm_alias()`, `nvm_alias_path()`
+- Creates text files containing the mapped version, named as the alias name
+- Special aliases: `default`, `node`, `iojs`, `stable`, `unstable` (note: `stable` and `unstable` are deprecated, from node's pre-v1 release plan)
+- Stored in `$NVM_DIR/alias/` directory
+
+#### `nvm current`
+- **Internal functions**: `nvm_ls_current()`
+- Shows currently active Node.js version
+- Returns "system" if using system Node.js
+
+#### `nvm which [version]`
+- **Internal functions**: `nvm_version_path()`, `nvm_resolve_alias()`
+- Shows path to specified Node.js version
+- Resolves aliases and version strings
+
+### Utility Commands
+
+#### `nvm cache clear|dir`
+- Cache management for downloaded binaries and source code
+- Clears or shows cache directory path
+
+#### `nvm debug`
+- Diagnostic information for troubleshooting
+- Shows environment, tool versions, and paths
+
+#### `nvm deactivate`
+- Removes nvm modifications from current shell
+- Restores original PATH
+
+#### `nvm unload`
+- Completely removes nvm from shell environment
+- Unsets all nvm functions and variables
+
+### Internal Function Categories
+
+#### Version Resolution
+- `nvm_resolve_alias()` - Resolves aliases to version numbers
+- `nvm_version()` - Finds best matching local version
+- `nvm_remote_version()` - Finds best matching remote version
+- `nvm_normalize_version()` - Standardizes version strings
+- `nvm_version_greater()` - Compares version numbers
+- `nvm_version_greater_than_or_equal_to()` - Version comparison with equality
+- `nvm_get_latest()` - Gets latest version from a list
+
+#### Installation Helpers
+- `nvm_install_binary()` - Downloads and installs precompiled binaries
+- `nvm_install_source()` - Compiles Node.js from source
+- `nvm_download_artifact()` - Downloads tarballs or binaries
+- `nvm_compute_checksum()` - Verifies download integrity
+- `nvm_checksum()` - Checksum verification wrapper
+- `nvm_get_mirror()` - Gets appropriate download mirror
+- `nvm_get_arch()` - Determines system architecture
+
+#### Path Management
+- `nvm_change_path()` - Updates PATH for version switching
+- `nvm_strip_path()` - Removes nvm paths from PATH
+- `nvm_version_path()` - Gets installation path for version
+- `nvm_version_dir()` - Gets version directory name
+- `nvm_prepend_path()` - Safely prepends to PATH
+
+#### Shell Detection and Compatibility
+- `nvm_is_zsh()` - Shell detection for zsh
+- `nvm_is_iojs_version()` - Checks if version is io.js
+- `nvm_get_os()` - Operating system detection
+- `nvm_supports_source_options()` - Checks if shell supports source options
+
+#### Network and Remote Operations
+- `nvm_download()` - Generic download function
+- `nvm_ls_remote()` - Lists remote versions
+- `nvm_ls_remote_iojs()` - Lists remote io.js versions
+- `nvm_ls_remote_index_tab()` - Parses remote version index
+
+#### Utility Functions
+- `nvm_echo()`, `nvm_err()` - Output functions
+- `nvm_has()` - Checks if command exists
+- `nvm_sanitize_path()` - Cleans sensitive data from paths
+- `nvm_die_on_prefix()` - Validates npm prefix settings
+- `nvm_ensure_default_set()` - Ensures default alias is set
+- `nvm_auto()` - Automatic version switching from .nvmrc
+
+#### Alias Management
+- `nvm_alias()` - Creates or lists aliases
+- `nvm_alias_path()` - Gets path to alias file
+- `nvm_unalias()` - Removes aliases
+- `nvm_resolve_local_alias()` - Resolves local aliases
+
+#### Listing and Display
+- `nvm_ls()` - Lists local versions
+- `nvm_ls_current()` - Shows current version
+- `nvm_tree_contains_path()` - Checks if path is in nvm tree
+- `nvm_format_version()` - Formats version display
+
+## Running Tests
+
+### Test Framework
+nvm uses the [urchin](https://www.npmjs.com/package/urchin) test framework for shell script testing.
+
+### Test Structure
+```
+test/
+├── fast/           # Quick unit tests
+├── slow/           # Integration tests
+├── sourcing/       # Shell sourcing tests
+├── install_script/ # Installation script tests
+├── installation_node/ # Node installation tests
+├── installation_iojs/ # io.js installation tests
+└── common.sh       # Shared test utilities
+```
+
+### Running Tests
+
+#### Install Dependencies
+```bash
+npm install  # Installs urchin, semver, and replace tools
+```
+
+#### Run All Tests
+```bash
+npm test               # Runs tests in current shell (sh, bash, dash, zsh, ksh)
+make test              # Runs tests in all supported shells (sh, bash, dash, zsh, ksh)
+make test-sh           # Runs tests only in sh
+make test-bash         # Runs tests only in bash
+make test-dash         # Runs tests only in dash
+make test-zsh          # Runs tests only in zsh
+make test-ksh          # Runs tests only in ksh
+```
+
+#### Run Specific Test Suites
+```bash
+make TEST_SUITE=fast test        # Only fast tests
+make TEST_SUITE=slow test        # Only slow tests
+make SHELLS=bash test            # Only bash shell
+```
+
+#### Individual Test Execution
+```bash
+./test/fast/Unit\ tests/nvm_get_arch     # Run single test (WARNING: This will exit/terminate your current shell session)
+./node_modules/.bin/urchin test/fast/                        # Run fast test suite
+./node_modules/.bin/urchin 'test/fast/Unit tests/nvm_get_arch'  # Run single test safely without shell termination
+./node_modules/.bin/urchin test/slow/                        # Run slow test suite
+./node_modules/.bin/urchin test/sourcing/                    # Run sourcing test suite
+```
+
+### Test Writing Guidelines
+- Tests should work across all supported shells (sh, bash, dash, zsh, ksh)
+- Define and use a `die()` function for test failures
+- Clean up after tests in cleanup functions
+- Mock external dependencies when needed
+- Place mocks in `test/mocks/` directory
+- Mock files should only be updated by the existing `update_test_mocks.sh` script, and any new mocks must be added to this script
+
+## Shell Environment Setup
+
+### Supported Shells
+- **bash** - Full feature support
+- **zsh** - Full feature support
+- **dash** - Basic POSIX support
+- **sh** - Basic POSIX support
+- **ksh** - Limited support (experimental)
+
+### Installing Shell Environments
+
+#### Ubuntu/Debian
+```bash
+sudo apt-get update
+sudo apt-get install bash zsh dash ksh
+# sh is typically provided by dash or bash and is available by default
+```
+
+#### macOS
+```bash
+# bash and zsh are available by default, bash is not the default shell for new user accounts
+# Install other shells via Homebrew
+brew install dash ksh
+# For actual POSIX sh (not bash), install mksh which provides a true POSIX sh
+brew install mksh
+```
+
+#### Manual Shell Testing
+```bash
+# Test in specific shell
+bash -c "source nvm.sh && nvm --version"
+zsh -c "source nvm.sh && nvm --version"
+dash -c ". nvm.sh && nvm --version"
+sh -c ". nvm.sh && nvm --version"          # On macOS: mksh -c ". nvm.sh && nvm --version"
+ksh -c ". nvm.sh && nvm --version"
+```
+
+### Shell-Specific Considerations
+- **zsh**: Requires basically any non-default zsh option to be temporarily unset to restore POSIX compliance
+- **dash**: Limited feature set, avoid bash-specific syntax
+- **ksh**: Some features may not work, primarily for compatibility testing
+
+## CI Environment Details
+
+### GitHub Actions Workflows
+
+#### `.github/workflows/tests.yml`
+- Runs test suite across multiple shells and test suites
+- Uses `script` command for proper TTY simulation
+- Matrix strategy covers shell × test suite combinations
+- Excludes install_script tests from non-bash shells
+
+#### `.github/workflows/shellcheck.yml`
+- Lints all shell scripts using shellcheck
+- Tests against multiple shell targets (bash, sh, dash, ksh)
+  - Note: zsh is not included due to [shellcheck limitations](https://github.com/koalaman/shellcheck/issues/809)
+- Uses Homebrew to install latest shellcheck version
+
+#### `.github/workflows/lint.yml`
+- Runs additional linting and formatting checks
+- Validates documentation and code style
+
+### Travis CI (Legacy)
+- Configured in `.travis.yml`
+- Tests on multiple Ubuntu versions
+- Installs shell environments via apt packages
+
+### CI Test Execution
+```bash
+# Simulate CI environment locally
+unset TRAVIS_BUILD_DIR  # Disable Travis-specific logic
+unset GITHUB_ACTIONS    # Disable GitHub Actions logic
+make test
+```
+
+## Setting Up shellcheck Locally
+
+### Installation
+
+#### macOS (Homebrew)
+```bash
+brew install shellcheck
+```
+
+#### Ubuntu/Debian
+```bash
+sudo apt-get install shellcheck
+```
+
+#### From Source
+```bash
+# Download from https://github.com/koalaman/shellcheck/releases
+wget https://github.com/koalaman/shellcheck/releases/download/latest/shellcheck-latest.linux.x86_64.tar.xz
+tar -xf shellcheck-latest.linux.x86_64.tar.xz
+sudo cp shellcheck-latest/shellcheck /usr/local/bin/
+```
+
+### Usage
+
+#### Lint Main Files
+```bash
+shellcheck -s bash nvm.sh
+shellcheck -s bash install.sh
+shellcheck -s bash nvm-exec
+shellcheck -s bash bash_completion
+```
+
+#### Lint Across Shell Types
+```bash
+shellcheck -s sh nvm.sh      # POSIX sh
+shellcheck -s bash nvm.sh    # Bash extensions
+shellcheck -s dash nvm.sh    # Dash compatibility
+shellcheck -s ksh nvm.sh     # Ksh compatibility
+```
+
+#### Common shellcheck Directives in nvm
+- `# shellcheck disable=SC2039` - Allow bash extensions in POSIX mode
+- `# shellcheck disable=SC2016` - Allow literal `$` in single quotes
+- `# shellcheck disable=SC2001` - Allow sed usage instead of parameter expansion
+- `# shellcheck disable=SC3043` - Allow `local` keyword (bash extension)
+
+### Fixing shellcheck Issues
+1. **Quoting**: Always quote variables: `"${VAR}"` instead of `$VAR`
+2. **POSIX compliance**: Avoid bash-specific features in portable sections
+3. **Array usage**: Use `set --` for positional parameters instead of arrays, which are not supported in POSIX
+4. **Local variables**: Declared with `local FOO` and then initialized on the next line (the latter is for ksh support)
+
+## Development Best Practices
+
+### Code Style
+- Use 2-space indentation
+- Follow POSIX shell guidelines for portability
+- Prefix internal functions with `nvm_`
+- Use `nvm_echo` instead of `echo` for output
+- Use `nvm_err` for error messages
+
+### Compatibility
+- Test changes across all supported shells
+- Avoid bash-specific features in core functionality
+- Use `nvm_is_zsh` to check when zsh-specific behavior is needed
+- Mock external dependencies in tests
+
+### Performance
+- Cache expensive operations (like remote version lists)
+- Use local variables to avoid scope pollution
+- Minimize subprocess calls where possible
+- Implement lazy loading for optional features
+
+### Debugging
+- Use `nvm debug` command for environment information
+- Enable verbose output with `set -x` during development
+- Test with `NVM_DEBUG=1` environment variable
+- Check `$NVM_DIR/.cache` for cached data issues
+
+## Common Gotchas
+
+1. **PATH modification**: nvm modifies PATH extensively; be careful with restoration
+2. **Shell sourcing**: nvm must be sourced, not executed as a script
+3. **Version resolution**: Aliases, partial versions, and special keywords interact complexly
+4. **Platform differences**: Handle differences between Linux, macOS, and other Unix systems
+5. **Network dependencies**: Many operations require internet access for version lists
+6. **Concurrent access**: Multiple shells can conflict when installing versions simultaneously
+
+## Windows Support
+
+nvm works on Windows via several compatibility layers:
+
+### WSL2 (Windows Subsystem for Linux)
+- Full nvm functionality available
+- **Important**: Ensure you're using WSL2, not WSL1 - see [Microsoft's WSL2 installation guide](https://docs.microsoft.com/en-us/windows/wsl/install) for up-to-date instructions
+- Install Ubuntu or other Linux distribution from Microsoft Store
+- Follow Linux installation instructions within WSL2
+
+### Cygwin
+- POSIX-compatible environment for Windows
+- Download Cygwin from [cygwin.com](https://www.cygwin.com/install.html) and run the installer
+- During installation, include these packages: bash, curl, git, tar, and wget
+- May require additional PATH configuration
+
+### Git Bash (MSYS2)
+- Comes with Git for Windows
+- Limited functionality compared to full Linux environment
+- Some features may not work due to path translation issues, including:
+  - Binary extraction paths may be incorrectly translated
+  - Symlink creation may fail
+  - Some shell-specific features may behave differently
+  - File permissions handling differs from Unix systems
+
+### Setup Instructions for Windows
+
+#### WSL2 (recommended)
+1. Install WSL2 using the official Microsoft guide: https://docs.microsoft.com/en-us/windows/wsl/install
+2. Install Ubuntu or preferred Linux distribution from Microsoft Store
+3. Follow standard Linux installation within WSL2
+
+#### Git Bash
+1. Install Git for Windows (includes Git Bash) from https://git-scm.com/download/win
+2. Open Git Bash terminal
+3. Run nvm installation script
+
+#### Cygwin
+1. Download and install Cygwin from https://www.cygwin.com/install.html
+2. Include bash, curl, git, tar, and wget packages during installation
+3. Run nvm installation in Cygwin terminal
+
+This guide should help GitHub Copilot understand the nvm codebase structure, testing procedures, and development environment setup requirements.

.github/workflows/windows-npm.yml

@@ -72,8 +72,11 @@ jobs:
             unset npm_config_prefix
             export NVM_INSTALL_GITHUB_REPO="$NVM_INSTALL_GITHUB_REPO"
             export NVM_INSTALL_VERSION="$NVM_INSTALL_VERSION"
+            export HOME="$(cygpath -u "$USERPROFILE")"
 
+            echo "HOME is $HOME"
             curl -fsSLo- "https://raw.githubusercontent.com/${NVM_INSTALL_GITHUB_REPO}/${NVM_INSTALL_VERSION}/install.sh" | bash
+            ls -l $HOME/.nvm
             . "$HOME/.nvm/nvm.sh"
             nvm install --lts
 

README.md

@@ -150,7 +150,7 @@ RUN touch "${BASH_ENV}"
 RUN echo '. "${BASH_ENV}"' >> ~/.bashrc
 
 # Download and install nvm
-RUN curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.2/install.sh | PROFILE="${BASH_ENV}" bash
+RUN curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | PROFILE="${BASH_ENV}" bash
 RUN echo node > .nvmrc
 RUN nvm install
 ```