📝 Add prompts for GitHub Copilot

.github/copilot-instructions.md

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+# Copilot Instructions
+
+## Architecture & Flow
+
+`bin/gtr` (961 lines) dispatches to `cmd_*` functions (case block lines 36‑77). Libraries sourced at startup:
+
+- `lib/core.sh` - create/list/remove/resolve worktrees
+- `lib/config.sh` - git config wrapper with precedence
+- `lib/ui.sh` - log_error/log_info/prompts
+- `lib/copy.sh` - glob pattern file copying
+- `lib/hooks.sh` - postCreate/postRemove execution
+- `lib/platform.sh` - OS detection + GUI helpers
+
+Adapters in `adapters/{editor,ai}` each implement two functions with strict contracts (see below).
+
+## Key Concepts
+
+- Special ID `1` = main repo (usable in `open`, `go`, `ai`).
+- Folder naming = sanitized branch (`feature/auth` → `feature-auth`).
+- Base dir resolution (`resolve_base_dir`): config `gtr.worktrees.dir` → env → default `<repo>-worktrees`; relative paths resolved from repo root; tilde expanded; warns if inside repo unignored.
+- Target resolution (`resolve_target`): ID `1` → current → sanitized path → scan directories; returns TSV: `is_main\tpath\tbranch`.
+- Config precedence (`cfg_default`): git config (local→global→system) → env → fallback. Multi-value keys merged & deduped (`cfg_get_all`).
+
+## Adapter Contract
+
+Editor: `editor_can_open`, `editor_open <path>`; AI: `ai_can_start`, `ai_start <path> [args...]`. Must check tool availability (`command -v`), emit errors via `log_error`, never silently fail, and avoid side effects outside the target directory (AI uses subshell `(cd ...)`). Update README, help (`cmd_help`), completions.
+
+## Manual Testing (Essential Subset)
+
+```bash
+./bin/gtr new feature/x      # creates folder feature-x
+./bin/gtr open feature/x     # loads configured editor
+./bin/gtr ai feature/x       # starts configured AI tool
+./bin/gtr list               # lists main + worktrees
+./bin/gtr rm feature/x       # removes worktree
+./bin/gtr go feature/x       # prints path (use in cd)
+```
+
+Advanced: `--force --name backend` (same branch multi-worktree); `git config --add gtr.copy.include "**/.env.example"`; hooks: `git config --add gtr.hook.postCreate "npm install"`.
+Full matrix: see `.github/instructions/testing.instructions.md`.
+
+## Common Changes
+
+**Add command**: new `cmd_<name>()` function in `bin/gtr` + case entry (lines 36‑77) + help text in `cmd_help` + all three completions (bash/zsh/fish) + README docs.
+
+**Add adapter**: two functions (see contract below), `log_error` with install instructions, quote all paths, check `command -v`. Update: README, help text (`cmd_help`), completions (all three).
+
+**Modify core (`lib/*.sh`)**: keep backwards compatibility, always quote variables `"$var"`, support Git <2.22 fallback (`branch --show-current` → `rev-parse --abbrev-ref HEAD`), test manually across macOS/Linux.
+
+## Patterns & Gotchas
+
+- Always quote paths (spaces). Avoid unguarded globbing.
+- `set -e` active: ensure non-critical failures are guarded (`command || true`).
+- Multi-value config keys require `git config --add` (do not overwrite entire list unintentionally).
+- If placing worktrees inside repo (relative path), add directory to `.gitignore` to prevent accidental commits.
+
+## Debugging
+
+Trace: `bash -x ./bin/gtr new test`; scoped: `set -x` / `set +x`; list function: `declare -f resolve_target`; inspect var: `echo "DEBUG=$var" >&2`; adapter sourcing: `bash -c 'source adapters/ai/claude.sh && ai_can_start && echo OK'`.
+
+## Troubleshooting Quick
+
+Permission: `chmod +x bin/gtr`. Missing adapter: `gtr adapter`. Install check: `./bin/gtr doctor`. Config issues: `git config --list | grep gtr`. Worktree confusion: inspect `resolve_target` logic & naming. Symlink problems: ensure `/usr/local/bin` exists then `ln -s "$(pwd)/bin/gtr" /usr/local/bin/gtr`.
+
+## Version
+
+Update `GTR_VERSION` (line 8 `bin/gtr`) when releasing; affects `gtr version` / `--version`.
+
+## Documentation Structure
+
+- **`.github/copilot-instructions.md`** (this file) - High-level guide for AI agents
+- **`.github/instructions/*.instructions.md`** - Specific guidance by file pattern:
+  - `testing.instructions.md` - Manual testing checklist (applies to: `bin/gtr`, `lib/**/*.sh`, `adapters/**/*.sh`)
+  - `sh.instructions.md` - Shell scripting conventions (applies to: `**/*.sh`, `**/*.bash`, `**/*.fish`)
+  - `lib.instructions.md` - Core library modification guidelines (applies to: `lib/**/*.sh`)
+  - `editor.instructions.md` - Editor adapter contract (applies to: `adapters/editor/**/*.sh`)
+  - `ai.instructions.md` - AI tool adapter contract (applies to: `adapters/ai/**/*.sh`)
+  - `completions.instructions.md` - Shell completion updates (applies to: `completions/*`)
+- **`README.md`** - User-facing documentation
+- **`CONTRIBUTING.md`** - Contribution guidelines
+- **`CLAUDE.md`** - Extended development guide for Claude Code
+
+Feedback: Ask if more detail needed on copy patterns, hooks, or multi-worktree `--force` safety.

.github/instructions/ai.instructions.md

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+---
+applyTo: adapters/ai/**/*.sh
+---
+
+# AI Instructions
+
+## Adding Features
+
+### New AI Tool Adapter (`adapters/ai/<name>.sh`)
+
+```bash
+#!/usr/bin/env bash
+# ToolName adapter
+
+ai_can_start() {
+  command -v tool-cli >/dev/null 2>&1
+}
+
+ai_start() {
+  local path="$1"
+  shift
+  if ! ai_can_start; then
+    log_error "ToolName not found. Install with: ..."
+    return 1
+  fi
+  (cd "$path" && tool-cli "$@")  # Note: subshell for directory change
+}
+```
+
+**Also update**: Same as editor adapters (README, completions, help text)
+
+## Contract & Guidelines
+
+- Must define: `ai_can_start` (0 = available), `ai_start <path> [args...]` (runs in subshell `(cd ...)`).
+- Always quote: `"$path"` and arguments; never assume current working directory.
+- Use `log_error` + helpful install hint; never silent fail.
+- Keep side effects confined to worktree directory; do not modify repo root unintentionally.
+- Accept extra args after `--`: preserve ordering (`ai_start` receives already-shifted args).
+- Prefer fast startup; heavy initialization belongs in hooks (`postCreate`), not adapters.
+- When adding adapter: update `cmd_help`, README tool list, and completions (bash/zsh/fish).
+- Test manually: `bash -c 'source adapters/ai/<tool>.sh && ai_can_start && echo OK'`.
+- Inspect function definition if needed: `declare -f ai_start`.

.github/instructions/completions.instructions.md

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+---
+applyTo: completions/gtr.bash, completions/_gtr, completions/gtr.fish
+---
+
+# Completions Instructions
+
+## Overview
+
+Shell completions provide tab-completion for `gtr` commands, flags, branches, and adapter names across Bash, Zsh, and Fish shells.
+
+## When to Update Completions
+
+**Always update all three completion files** when:
+
+- Adding new commands (e.g., `gtr new-command`)
+- Adding new flags to existing commands (e.g., `--new-flag`)
+- Adding editor or AI adapters (completion must list available adapters)
+- Changing command names or flag names
+
+## File Responsibilities
+
+- **`completions/gtr.bash`** - Bash completion (requires bash-completion v2+)
+- **`completions/_gtr`** - Zsh completion (uses Zsh completion system)
+- **`completions/gtr.fish`** - Fish shell completion
+
+## Implementation Pattern
+
+Each completion file implements:
+
+1. **Command completion** - Top-level commands (`new`, `rm`, `open`, `ai`, `list`, etc.)
+2. **Flag completion** - Command-specific flags (e.g., `--from`, `--force`, `--editor`)
+3. **Branch completion** - Dynamic completion of existing worktree branches (via `gtr list --porcelain`)
+4. **Adapter completion** - Editor names (`cursor`, `vscode`, `zed`) and AI tool names (`aider`, `claude`, `codex`)
+
+## Testing Completions
+
+**Manual testing** (no automated tests):
+
+```bash
+# Bash - source the completion file
+source completions/gtr.bash
+gtr <TAB>                    # Should show commands
+gtr new <TAB>                # Should show flags
+gtr open <TAB>               # Should show branches
+gtr open --editor <TAB>      # Should show editor names
+
+# Zsh - fpath must include completions directory
+fpath=(completions $fpath)
+autoload -U compinit && compinit
+gtr <TAB>
+
+# Fish - symlink to ~/.config/fish/completions/
+ln -s "$(pwd)/completions/gtr.fish" ~/.config/fish/completions/
+gtr <TAB>
+```
+
+## Branch Completion Logic
+
+All three completions dynamically fetch current worktree branches:
+
+- Parse output of `gtr list --porcelain` (tab-separated: `path\tbranch\tstatus`)
+- Extract branch column (second field)
+- Exclude the special ID `1` (main repo) if needed
+
+## Adapter Name Updates
+
+When adding an editor or AI adapter:
+
+**Bash** (`completions/gtr.bash`):
+
+- Update `_gtr_editors` array or case statement
+- Update flag completion for `--editor` in `open` command
+
+**Zsh** (`completions/_gtr`):
+
+- Update `_arguments` completion specs for `--editor` or `--ai`
+- Use `_values` or `_alternative` for adapter names
+
+**Fish** (`completions/gtr.fish`):
+
+- Update `complete -c gtr` lines for editor/AI flags
+- List adapter names explicitly or parse from `gtr adapter` output
+
+## Keep in Sync
+
+The three completion files must stay synchronized:
+
+- Same commands supported
+- Same flags for each command
+- Same adapter names
+- Same branch completion behavior
+
+## Examples
+
+**Adding a new command `gtr status`**:
+
+1. Add `status` to main command list in all three files
+2. Add flag completion if the command has flags
+3. Test tab completion works
+
+**Adding a new editor `sublime`**:
+
+1. Create `adapters/editor/sublime.sh` with contract functions
+2. Add `sublime` to editor list in all three completion files
+3. Update help text in `bin/gtr` (`cmd_help` function)
+4. Update README with installation instructions
+5. Test `gtr open --editor s<TAB>` completes to `sublime`
+
+## Common Pitfalls
+
+- **Forgetting to update all three files** - Always update Bash, Zsh, AND Fish
+- **Hardcoding adapter names** - Keep adapter lists in sync with actual files in `adapters/{editor,ai}/`
+- **Not testing** - Source/reload completions and test with `<TAB>` key
+- **Case sensitivity** - Command and flag names must match exactly (case-sensitive)
+
+## Bash-Specific Notes
+
+- Requires `bash-completion` v2+ package
+- Use `COMPREPLY` array to return completions
+- Use `compgen` to filter based on current word (`$cur`)
+- Check `$COMP_CWORD` for argument position
+
+## Zsh-Specific Notes
+
+- Uses `_arguments` completion framework
+- Supports more sophisticated completion logic (descriptions, grouping)
+- Use `_describe` for simple lists, `_arguments` for complex commands
+
+## Fish-Specific Notes
+
+- Uses declarative `complete -c gtr` syntax
+- Conditions can check previous arguments with `__fish_seen_subcommand_from`
+- Can call external commands for dynamic completion

.github/instructions/editor.instructions.md

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+---
+applyTo: adapters/editor/**/*.sh
+---
+
+# Editor Instructions
+
+## Adding Features
+
+### New Editor Adapter (`adapters/editor/<name>.sh`)
+
+```bash
+#!/usr/bin/env bash
+# EditorName adapter
+
+editor_can_open() {
+  command -v editor-cli >/dev/null 2>&1
+}
+
+editor_open() {
+  local path="$1"
+  if ! editor_can_open; then
+    log_error "EditorName not found. Install from https://..."
+    return 1
+  fi
+  editor-cli "$path"
+}
+```
+
+**Also update**:
+
+- README.md (setup instructions)
+- All three completion files: `completions/gtr.bash`, `completions/_gtr`, `completions/gtr.fish`
+- Help text in `bin/gtr` (`cmd_help` function)
+
+## Contract & Guidelines
+
+- Required functions: `editor_can_open` (probe via `command -v`), `editor_open <path>`.
+- Quote all paths; support spaces. Avoid changing PWD globally—no subshell needed (editor opens path).
+- Use `log_error` with actionable install guidance if command missing.
+- Keep adapter lean: no project scans, no blocking prompts.
+- Naming: file name = tool name (`zed.sh` → `zed` flag). Avoid uppercase.
+- Update: README editor list, completions (bash/zsh/fish), help (`Available editors:`), optional screenshots.
+- Manual test: `bash -c 'source adapters/editor/<tool>.sh && editor_can_open && editor_open . || echo fail'`.
+- Fallback behavior: if editor absent, fail clearly; do NOT silently defer to file browser.
+- Inspect function definition if needed: `declare -f editor_open`.

.github/instructions/lib.instructions.md

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+---
+applyTo: lib/**/*.sh
+---
+
+# Lib Instructions
+
+## Modifying Core (`lib/*.sh`)
+
+- **Maintain backwards compatibility** with existing configs
+- **Quote all paths**: Support spaces in directory names
+- **Use `log_error` / `log_info`** from `lib/ui.sh` for user messages
+- **Git version fallbacks**: Check `lib/core.sh:97-100` for example (Git 2.22+ `--show-current` vs older `rev-parse`)
+
+## Key Functions & Responsibilities
+
+- `resolve_base_dir`: config/env/default selection; warn if inside repo & not ignored.
+- `resolve_target`: ID `1` + branch/current + sanitized path scan; returns TSV.
+- `create_worktree`: decides remote/local/new; respects `--force` + `--name` safety.
+- `cfg_default`: precedence local→global→system→env→fallback (do not reorder).
+- `cfg_get_all`: merge multi-value keys; preserves order; deduplicates.
+
+## Change Guidelines
+
+- Preserve adapter contracts; do not rename exported functions used by `bin/gtr`.
+- Add new config keys with `gtr.<name>` prefix; avoid collisions.
+- For performance-sensitive loops (e.g. directory scans) prefer built-ins (`find`, `grep`) with minimal subshells.
+- Any new Git command: add fallback for older versions or guard with detection.
+- Manual test after changes (subset): `new`, `open`, `ai`, `rm`, `list --porcelain`, `config set/get/unset`, `go 1`, hooks run once.

.github/instructions/sh.instructions.md

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+---
+applyTo: **/*.bash, **/*.fish, **/*.sh
+---
+
+# Shell Instructions
+
+## Architecture
+
+**Key Pattern**: Everything is sourced at startup (`set -e` enabled). Functions call each other directly. No subshells except for hooks and AI tools.
+
+## Code Conventions
+
+### Shell Script Style
+
+- **Bash 3.2+ compatible** (macOS default), but 4.0+ features allowed where appropriate
+- **Always quote variables**: `"$var"` not `$var`
+- **Function-scoped vars**: Use `local var="value"`
+- **Error handling**: Check return codes; functions return 1 on failure
+- **Naming**: `snake_case` for functions/vars, `UPPER_CASE` for constants
+
+### Strict Mode & Safety
+
+- Global `set -e` in `bin/gtr`: guard non-critical commands with `|| true`.
+- Prefer `[ ]` over `[[ ]]` for POSIX portability (use `[[` only when needed).
+- Always quote glob inputs; disable unintended globbing (`set -f` temporarily if required).
+
+### Portability
+
+- Target Bash 3.2+: avoid associative arrays; use simple string/loop constructs.
+- Avoid `readarray` and process substitution unsupported in older Bash.
+
+### Debugging
+
+- Quick trace: `bash -x ./bin/gtr <cmd>`.
+- Inline: wrap suspicious block with `set -x` / `set +x`.
+- Function presence: `declare -f create_worktree` or `declare -f resolve_target`.
+- Variable inspection: `echo "DEBUG var=$var" >&2` (stderr keeps stdout clean for command substitution).
+
+### External Commands
+
+- Keep dependencies minimal: only `git`, `sed`, `awk`, `find`, `grep` (avoid jq/curl unless justified).
+- Check availability before use if adding new tools.
+
+### Quoting & Paths
+
+- Use `"${var}"`; for loop over lines: `while IFS= read -r line; do ... done` to preserve spaces.
+- Sanitize branch names via `sanitize_branch_name` (do NOT duplicate logic elsewhere).