refactor: drop typer, build the CLI directly on click

[shcheklein]

Follow-up to #497 — implements the mitigation plan from the typer discussion there: remove typer entirely instead of migrating to its vendored-click API. Net: -1 dependency, -1 pin, net -7 lines, and immunity to typer's release churn.

Why dropping typer (not migrating to typer ≥0.26)

gto only used typer's thin core — declaring command params via function signatures. Everything that defines the CLI's actual behavior (sectioned help, command aliases, "Examples:" epilogs, the unified error funnel) was already hand-written click code. So the migration is mechanical: re-express ~10 command signatures as click decorators, delete the typer layer.

What changed

• Every command's params moved from typer Argument/Option defaults to @click.option/@click.argument decorators. Flags, defaults, help texts, callbacks, exit codes: unchanged.
• app is now a click.Group (same gto.cli:app entry point).
• typer.Exit/typer.colors/typer.BadParameter → click equivalents.
• New GtoArgument(click.Argument) carries argument help (click has no native argument help) and GtoCliMixin.format_options renders an "Arguments" section — so test_commands_args_help still enforces help on every param.
• GtoGroup.list_commands override keeps definition order (click sorts alphabetically by default).
• Tests: typer.testing.CliRunner → click.testing.CliRunner; the get_command_from_info fixture becomes app.commands.values().
• Dead option definitions from long-removed commands dropped (--rev, --all, --expected, --type, --path, --description, --custom, --table, --commit, --push-commit, --branch, arg_version, arg_stage, option_version, option_to_version, GTOGroupSection).
• pyproject.toml: typer removed; click>=8.2,<9 (8.2 floor for CliRunner without mix_stderr and kebab-case command naming).

User-visible changes

• Top-level gto --help output is byte-identical to before.
• Subcommand --help switches from typer's rich boxes to click's classic plain format (matching the top-level help style), with an added "Arguments" section preserving argument descriptions. Everything else — usage lines, option lists, defaults — carries over.

Verification

• pre-commit run --all-files green (ruff, mypy 2.2.0, pylint 4.0.6).
• 165/165 tests pass on Python 3.10, 3.13, 3.14 (fresh venvs; typer confirmed absent).
• End-to-end CLI exercise in a scratch repo: register, assign (via promote alias), show (table + --json), check-ref, history --plain, deprecate; error paths verified — GTOException → ❌ message + exit 1, usage error → exit 2, -h works on subcommands.
• Warning count in pytest dropped 27 → 1 (typer's click-compat deprecation warnings gone).

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 99.16667% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
gto/cli.py	99.16%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[shcheklein]

Post-migration review round (commit 98e8f04):

Manual output review of every command — ran the full command surface (~40 invocations: register/assign/promote/deprecate flows, all show/history/check-ref/stages output modes, parse-tag, print-state, doctor, plus error paths) under both the pre-migration build (main @ 21f6a8a, typer 0.25.1) and this branch, and diffed normalized outputs. Byte-identical on every success path. Only differences are in usage-error decoration: click's plain Error: ... line instead of typer's rich ╭─ Error ─╮ box, and the hint text suggests --help instead of -h (both flags work). Same messages, same exit codes.

Coverage — gto/cli.py was at 85% after the migration; the uncovered lines included real regression-sensitive paths (notably the promote alias resolution, which no test exercised). Added 23 tests: alias, subcommand help + "Arguments" section, Examples epilog, --version/-v/--traceback, click-exception passthrough, --simple/--sort validation, assign/deprecate branch paths, all --json modes, parse-tag --key, multi-event refs, show --ref mismatch, print-state, doctor with broken config, unknown command. gto/cli.py: 85% → 97% (project total 86% → 88%; 165 → 188 tests). The 9 remaining uncovered lines are defensive fallbacks, completion-mode resilient_parsing returns, and __main__.

Critical review fixes — deprecate's version/stage params correctly annotated Optional[str]; removed the "Manage artifact enrichments" help section (dead since the enrichment commands were removed); minor paren cleanup. One observation left as-is: doctor's except WrongConfig around the CONFIG repr is unreachable in practice (module-level CONFIG falls back to defaults on parse errors; the failure surfaces later via _get_state → ❌ exit 1, which is now covered by a test) — left the defensive branch alone.

[Copilot]

Pull request overview

Refactors gto’s CLI implementation to remove the typer dependency and define the CLI directly using click, aligning with the mitigation plan from #497 and reducing exposure to typer’s release changes.

Changes:

• Replaced the Typer-based CLI with a Click-based app (click.Group), including custom help formatting (Arguments section, Examples epilog) and command ordering/alias handling.
• Updated tests to use click.testing.CliRunner and to validate new/maintained CLI behaviors (version flag, aliasing, help rendering, exception pass-through).
• Updated pyproject.toml dependencies to drop typer and require click>=8.2,<9.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
gto/cli.py	Rebuilds the CLI on Click (group/commands/options/arguments), preserves help structure via custom formatter/argument class, and keeps unified error handling + aliases.
pyproject.toml	Removes typer and bumps Click lower bound to 8.2.
tests/conftest.py	Switches runner infrastructure to Click’s CliRunner.
tests/test_cli.py	Updates fixtures for Click command discovery and adds/adjusts CLI behavior tests (help rendering, version flag, aliases, exception behavior).
tests/test_config.py	Migrates from Typer’s runner to Click’s runner for help invocation.

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[shcheklein]

Agreed — fixed in #503 (the PR merged before this could land here): params now annotated to match the callback return types (Optional[bool] / VersionSort), and the # type: ignore comments those wrong annotations forced are gone. mypy passes without any ignores.

[shcheklein]

Agreed — fixed in #503 (the PR merged before this could land here): params now annotated to match the callback return types (Optional[bool] / VersionSort), and the # type: ignore comments those wrong annotations forced are gone. mypy passes without any ignores.

[shcheklein]

Agreed — fixed in #503 (the PR merged before this could land here): params now annotated to match the callback return types (Optional[bool] / VersionSort), and the # type: ignore comments those wrong annotations forced are gone. mypy passes without any ignores.

[shcheklein]

Agreed — fixed in #503 (the PR merged before this could land here): params now annotated to match the callback return types (Optional[bool] / VersionSort), and the # type: ignore comments those wrong annotations forced are gone. mypy passes without any ignores.