Add Google's Antigravity support

[ivanviragine]

Pull Request

Description

Add Google Antigravity as a built-in editor adapter. Antigravity uses the agy CLI command, is classified as a standard (GUI) editor type, and supports the workspace flag for .code-workspace file detection — similar to VS Code and Cursor.

Also fixes a pre-existing bug in scripts/generate-completions.sh where the gtr.ui.color config key was missing its fish completion description, causing it to fall through to the default $key echo instead of a human-readable label.

Motivation

Antigravity is a workspace-aware GUI editor that integrates well with git gtr's worktree workflow. Adding it as a built-in adapter lets users configure it with git gtr config set gtr.editor.default antigravity and have it work out of the box with workspace file support, consistent help text, and shell completions.

The fish completion fix ensures gtr.ui.color displays the correct description (Color output mode (auto, always, never)) instead of the raw key name when tab-completing config keys.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring (no functional changes)
• Other (please describe):

Testing

Manual Testing Checklist

Tested on:

• macOS
• Linux (specify distro: ______)
• Windows (Git Bash)

Core functionality tested:

• git gtr new <branch> - Create worktree
• git gtr go <branch> - Navigate to worktree
• git gtr editor <branch> - Open in editor (if applicable)
• git gtr ai <branch> - Start AI tool (if applicable)
• git gtr rm <branch> - Remove worktree
• git gtr list - List worktrees
• git gtr config - Configuration commands (if applicable)
• Other commands affected by this change: git gtr adapter, git gtr help editor

Test Steps

1. Run existing BATS test suite: all 236/236 tests pass with no regressions
2. Run git gtr adapter and verify antigravity appears in the editor list
3. Run git gtr help editor and verify antigravity is listed among available editors
4. Run ./scripts/generate-completions.sh --check and verify completions are in sync
5. Verify fish completion for gtr.ui.color now shows "Color output mode (auto, always, never)" description

Expected behavior: Antigravity appears as a built-in editor option in all help, adapter, completion, and configuration surfaces. Fish completion for gtr.ui.color shows the correct description.

Actual behavior: Matches expected behavior.

Breaking Changes

• This PR introduces breaking changes
• I have discussed this in an issue first
• Migration guide is included in documentation

Checklist

Before submitting this PR, please check:

• I have read CONTRIBUTING.md
• My code follows the project's style guidelines
• I have performed manual testing on at least one platform
• I have updated documentation (README.md, CLAUDE.md, etc.) if needed
• My changes work on multiple platforms (or I've noted platform-specific behavior)
• I have added/updated shell completions (if adding new commands or flags)
• I have tested with both git gtr (production) and ./bin/gtr (development)
• No new external dependencies are introduced (Bash + git only)
• All existing functionality still works

Additional Context

Files changed:

• lib/adapters.sh — Added antigravity entry to _EDITOR_REGISTRY (command: agy, type: standard, flags: workspace)
• lib/commands/help.sh — Added antigravity to editor option lists in _help_editor and _help_full
• README.md — Added antigravity to editor references
• docs/configuration.md — Added antigravity to editor configuration documentation
• completions/gtr.bash, completions/_git-gtr, completions/git-gtr.fish — Regenerated via scripts/generate-completions.sh
• scripts/generate-completions.sh — Added missing gtr.ui.color case to fish completion description generator

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License Acknowledgment

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache License 2.0.

Summary by CodeRabbit

• New Features
  • Added Antigravity editor support with full integration across all editor selection mechanisms
  • Enhanced worktree opening behavior with improved fallback detection
• Documentation
  • Updated editor configuration guides to include Antigravity installation instructions
  • Updated all editor references to include Antigravity alongside existing options

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Walkthrough

The pull request adds support for a new editor called Antigravity throughout the tool by registering it as an adapter, updating documentation, and extending shell completion scripts to include it alongside existing editors.

Changes

Cohort / File(s)	Summary
Documentation Updates CLAUDE.md, README.md, docs/configuration.md	Adds Antigravity to editor lists, integration references, and setup instructions across documentation.
Shell Completions completions/_git-gtr, completions/git-gtr.fish, completions/gtr.bash	Extends editor completion options to include antigravity for bash, fish, and zsh-style shells.
Adapter and Help Code lib/adapters.sh, lib/commands/help.sh	Registers new Antigravity editor adapter with command agy and updates help text to reflect the new editor option.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A gravity-defying gift we bring,
Antigravity floats on swift wing,
Through scripts and docs it rises high,
New editor options reach the sky! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 71.43% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Add Google's Antigravity support' clearly and concisely summarizes the main change: adding Antigravity as a built-in editor adapter to the git-worktree-runner project.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@lib/adapters.sh`:
- Line 20: The registry entry string in lib/adapters.sh currently tells users to
install agy from "https://antigravity.google" which is incorrect; update the
error message for the "antigravity|agy|standard|Antigravity 'agy' command not
found..." entry to instruct users to install the `agy` CLI from within the
Antigravity application (e.g., via Antigravity's onboarding or Settings) rather
than pointing to an external URL, and keep the rest of the registry entry format
and placement unchanged.