extract-facade-from-base-lib

name	extract-facade-from-base-lib
description	Migrates a public method from Git::Base or Git::Lib to a Git::Repository facade method (under lib/git/repository/) as part of the v5.0.0 architectural redesign. Use when extracting a specific public method during the Strangler Fig migration of Git::Base / Git::Lib into Git::Repository.

Extract Facade from Base/Lib

Migrate an existing public method from Git::Base and/or Git::Lib to a Git::Repository::* facade method. This is the second extraction step of the v5.0.0 redesign — it follows Extract Command from Lib, which moves the underlying CLI invocation into a Git::Commands::* class.

In Phase 4 of the redesign, both Git::Base and Git::Lib will be deleted. This migration moves their public surface to Git::Repository. Until Phase 4, the original methods remain in place and delegate to the new facade method to preserve backward compatibility within the migration window.

Contents

• Contents
• How to use this skill
• Prerequisites
• Related skills
• Input
• Source patterns
  • Pattern A — Git::Base wrapper + Git::Lib implementation
  • Pattern B — Git::Lib-only (public-by-exposure)
  • Pattern C — Git::Base-only (no Git::Lib method)
• Determining the option allowlist
• Workflow
  • Branch setup
  • Step 1 — Identify the source pattern
  • Step 2 — Plan the migration and get approval
  • Step 3 — Ensure adequate legacy tests
  • Step 4 — Ensure the underlying Git::Commands::* class exists
  • Step 5 — Implement the facade method
  • Step 6 — Update Git::Base and/or Git::Lib to delegate
• Commit discipline
• Quality gates
• What stays vs. what moves
• Review mode
  • Invoke
  • R1 — Source analysis
  • R2 — Legacy test coverage
  • R3 — Command class
  • R4 — Facade implementation
  • R5 — Delegation
  • R6 — Quality gates

How to use this skill

Attach this file to your Copilot Chat context, then invoke with the public method to migrate. Examples:

Using the Extract Facade from Base/Lib skill, migrate Git::Base#commit to
Git::Repository#commit.

Extract Facade: Git::Lib#branches_all (called publicly via g.lib.branches_all)

Prerequisites

Before starting, you MUST load the following skill(s):

• Facade Implementation — drives the actual scaffolding of the new facade method
• YARD Documentation — baseline YARD rules

Related skills

• Facade Implementation — used in Step 5 to scaffold the new facade method
• Facade Test Conventions — unit and integration test conventions for the new facade method
• Facade YARD Documentation — YARD docs for the new facade module/method
• Extract Command from Lib — sibling extraction skill that moves the underlying CLI call into a Git::Commands::* class. Run first when no command class exists yet.
• Command Implementation — used in Step 4 if a new Git::Commands::* class needs to be scaffolded
• Project Context — three-layer architecture and Phase 4 deletion plan

Input

Required:

1. The Git::Base and/or Git::Lib public method to migrate.
2. The git operation it performs (subcommand + flags).

Source patterns

Public methods being migrated fall into one of three patterns. Identify which pattern applies before planning the migration.

Pattern A — Git::Base wrapper + Git::Lib implementation

The most common pattern. Git::Base#foo is a thin wrapper that forwards to Git::Lib#foo, which contains the orchestration logic.

Examples: commit, diff_full, branches, worktree_add.

# lib/git/base.rb
def commit(message, opts = {})
  self.lib.commit(message, opts)
end

# lib/git/lib.rb
def commit(message, opts = {})
  opts = opts.merge(message: message) if message
  deprecate_commit_no_gpg_sign_option!(opts)
  Git::Commands::Commit.new(self).call(edit: false, **opts).stdout
end

Public contract source: Git::Base#commit signature; Git::Lib#commit implementation.

When migrating, the facade method must preserve this signature exactly (e.g. commit(message, opts = {})) — even though greenfield facade methods would prefer **options per facade-implementation REFERENCE.md — Choosing the method signature. The legacy public contract wins during migration.

Pattern B — Git::Lib-only (public-by-exposure)

The public API is g.lib.foo — Git::Base exposes Git::Lib as #lib (or through a similar accessor), so Git::Lib methods are reachable as public API even when no Git::Base wrapper exists.

Examples: branches_all, worktrees_all, current_branch_state.

# lib/git/lib.rb (no Git::Base wrapper exists)
def branches_all
  result = Git::Commands::Branch::List.new(self).call(all: true, format: ...)
  Git::Parsers::Branch.parse_list(result.stdout)
end

Public contract source: Git::Lib#foo signature and implementation.

Migration consequence: After Phase 4, callers using g.lib.foo must migrate to g.foo (or g.repository.foo). Document this in the migration plan.

Pattern C — Git::Base-only (no Git::Lib method)

The implementation lives entirely in Git::Base with no Git::Lib counterpart. The method may call command(...) directly via lib.send(...) or implement filesystem operations.

Examples: add_remote, with_index, repo_size, archive.

# lib/git/base.rb
def repo_size
  all_files_size = 0
  Find.find(repo.path) { |f| all_files_size += File.size(f) if File.file?(f) }
  all_files_size
end

Public contract source: Git::Base#foo signature and implementation.

Determining the option allowlist

When the facade method uses assert_valid_opts!, the allowlist (*_ALLOWED_OPTS) must contain only the options that were accepted in the 4.x branch of this gem. Do not expand the allowlist to match everything the underlying Git::Commands::* class supports — new options are deferred to a follow-up PR so they can be properly documented and tested.

How to find the 4.x allowlist for a method:

1. Open https://github.com/ruby-git/ruby-git/blob/4.x/lib/git/lib.rb and search for the method's *_OPTION_MAP constant (e.g. ADD_OPTION_MAP, RESET_OPTION_MAP).
2. The option keys declared in that map are the only keys that were valid in 4.x. Any key not present in the map would have raised ArgumentError via ArgsBuilder.validate! — confirmed by https://github.com/ruby-git/ruby-git/blob/4.x/lib/git/args_builder.rb.
3. Use those keys — and only those keys — in the facade's *_ALLOWED_OPTS constant, @option YARD tags, and integration/unit tests.
4. If the underlying Git::Commands::* class supports additional options beyond the 4.x map, note them in a follow-up issue rather than silently including them.

Workflow

Branch setup

All work must be done on a feature branch. Never commit or push directly to main.

git checkout -b <feature-branch-name>

Step 1 — Identify the source pattern

1. Locate the public method in Git::Base and/or Git::Lib.

2. Determine which Source pattern applies (A, B, or C).

3. Note:

   • the public signature (positional args, options hash, keyword args)
   • the exact return value of the legacy method — read the source code to see whether it ends in .stdout, .stdout.chomp, a parser call, a domain object, nil, etc. Do not assume from the YARD @return tag, which may be stale or missing. The facade must reproduce this exact value (e.g. if Git::Lib#add ends in .stdout, the facade returns String, not Git::CommandLineResult).
   • any pre-processing (path expansion, option whitelisting, deprecation handling)
   • any post-processing (parsing, result-class assembly)
   • any execution-context arguments (timeout:, chdir:, env:)
   • the 4.x-supported options: locate the corresponding *_OPTION_MAP constant in 4.x/lib/git/lib.rb and record which option keys it declared. These become the facade's *_ALLOWED_OPTS allowlist — see Determining the option allowlist.

4. Document the method's current public contract in writing — it must be preserved exactly by the facade method.

5. Run linters and rubocop to confirm a clean baseline:

   bundle exec rubocop
   

Step 2 — Plan the migration and get approval

Before writing or changing any code, present a migration plan and wait for explicit confirmation from the user.

The plan must include:

Public method	Source pattern	Underlying command class	Class exists?	Target facade module	Notes
Git::Base#foo	A / B / C	Git::Commands::Foo	✅ / 🆕	Git::Repository::Topic (existing or new)	mapping decisions

Also state:

• The exact public contract to preserve (signature + return type + raised errors).
• Whether a new topic module is required (justify per facade-implementation REFERENCE.md). When extracting one method at a time, scan Git::Base / Git::Lib for siblings on the same git topic and check redesign/3_architecture_implementation.md before deciding — see One-at-a-time extraction.
• The delegation strategy for Git::Base and/or Git::Lib (Step 6) — both remain in place during the migration window and delegate to the new facade.
• For Pattern B: explicit note that g.lib.foo callers will need to migrate before Phase 4; capture this as a follow-up issue or CHANGELOG entry.

Then ask:

Does this mapping look correct? Any changes before I start implementing?

Do not move to Step 3 until the user confirms the plan.

Step 3 — Ensure adequate legacy tests

Verify that legacy tests in tests/units/ and existing specs in spec/ adequately cover the public method. The legacy tests guarantee the migration preserves backward compatibility.

1. Search for coverage:

   grep -rn '<method_name>' tests/units/ spec/
   

2. If coverage is insufficient, add minimal new tests that exercise the current public contract. Use existing legacy test conventions for Test::Unit tests in tests/units/. Do not change existing tests.

3. Run the new tests and rubocop:

   bundle exec bin/test <test-file-basename>
   bundle exec rubocop tests/units/<test-file>
   

4. Commit:

   git commit -m "refactor(test): add legacy tests for <method_name>"
   

Step 4 — Ensure the underlying Git::Commands::* class exists

The facade method calls one or more Git::Commands::* classes. If any required command class does not exist yet, scaffold it first using Extract Command from Lib (which in turn uses Command Implementation).

For Pattern C migrations, the source Git::Base method may not currently call through a Git::Commands::* class at all (it uses command(...) directly or filesystem operations). In that case, you must scaffold the Git::Commands::* class before this step.

Skip this step when every required command class already exists.

Step 5 — Implement the facade method

Delegate to the Facade Implementation skill in Scaffold or Update mode. That skill handles:

• topic module selection
• generating or extending lib/git/repository/<topic>.rb
• generating or extending spec/unit/git/repository/<topic>_spec.rb
• generating or extending spec/integration/git/repository/<topic>_spec.rb
• YARD documentation
• running facade-side quality gates

The new facade method must preserve the source method's public contract exactly — same signature, same return type, same raised errors. Use the exact return type the source method documented (String, Array, Hash, domain object, CommandLineResult).

For Pattern A and B migrations, copy any pre-processing logic (option whitelisting, deprecation rewrites, key normalization) from Git::Lib to the facade method. Do not leave it behind in Git::Lib — the facade is now the source of truth.

When copying option whitelisting logic, use only the keys from the 4.x *_OPTION_MAP for the *_ALLOWED_OPTS constant — do not expand to match the full Git::Commands::* argument DSL. See Determining the option allowlist.

For Pattern C migrations, port any pre-processing or filesystem logic from Git::Base to the facade method.

After the facade method is in place and tests pass, commit:

git commit -m "feat(repository): add Git::Repository#<method_name> facade method"

Step 6 — Update Git::Base and/or Git::Lib to delegate

The original methods stay in place during the migration window and delegate to the new facade method. Both Git::Base and Git::Lib will be deleted in Phase 4; until then, delegation preserves backward compatibility.

For each source pattern, the delegation looks like:

Pattern A — both files delegate:

# lib/git/base.rb — already a wrapper; redirect to repository
def commit(message, opts = {})
  repository.commit(message, opts)
end

# lib/git/lib.rb — keep public-by-exposure callers working
def commit(message, opts = {})
  @repository.commit(message, opts)
end

Pattern B — Git::Lib delegates:

# lib/git/lib.rb
def branches_all
  @repository.branches_all
end

Pattern C — Git::Base delegates:

# lib/git/base.rb
def add_remote(name, url, opts = {})
  repository.add_remote(name, url, opts)
end

(The exact accessor — repository, @repository, self.repository — depends on how Git::Base and Git::Lib hold their reference to the new Git::Repository instance during the migration window. Match the existing pattern used by other migrated methods.)

After delegation is in place, verify:

bundle exec bin/test <legacy-test-file-basename>
bundle exec rspec
bundle exec rubocop
bundle exec rake yard

Commit:

git commit -m "refactor(base): delegate <method_name> to Git::Repository"

(Use refactor(lib): if only Git::Lib was updated. When both files change, use two separate commits — one per scope — to keep each commit single-scoped.)

Commit discipline

Keep work organized into three logical commit categories (each optional if no changes were needed for that step):

1. refactor(test): add legacy tests for <method_name> — new tests in tests/units/ (Step 3)
2. feat(repository): add Git::Repository#<method_name> facade method — new facade module/method, unit specs, integration specs (Step 5)
3. refactor(base): delegate <method_name> to Git::Repository — Git::Base updated to delegate (Step 6); use refactor(lib): if only Git::Lib changed. When both files change, prefer two separate commits — one per scope — so each commit has a single conventional-commits scope.

If a new Git::Commands::* class was scaffolded in Step 4, it gets its own commit (refactor(command): add Git::Commands::<Command> class) per Extract Command from Lib.

Issue and PR references in commit bodies: Do not use #<number> in the commit body — write issue 1000 not issue #1000. To close an issue/PR, use Closes/Fixes/Resolves #<number> in the footer.

If further changes are needed after task commits are created, amend into the appropriate commit and rebase. Always verify quality gates pass after rebasing.

Quality gates

Run the gates discovered from the project's parallel default task at every step:

bundle exec ruby -e "require 'rake'; load 'Rakefile'; puts Rake::Task['default:parallel'].prerequisites"

Run each listed task individually via bundle exec rake <task> and fix failures before advancing. All listed tasks must pass before committing.

What stays vs. what moves

Stays in Git::Base / Git::Lib until Phase 4:

• Delegating methods — one-line forwards to the new Git::Repository facade method, preserving backward compatibility during the migration window.
• Methods not yet migrated — original implementation remains until extracted.

Moves to Git::Repository::*:

• The full public contract (signature, return type, raised errors).
• All pre-processing logic (option whitelisting, deprecation handling, key normalization, defaults).
• All post-processing logic (parsing, result-class assembly).
• The YARD docs that document the public API.

Branch workflow: Implement migrations on a feature branch. Never commit or push directly to main — open a pull request when changes are ready to merge.

Review mode

Use this checklist to audit a completed extraction PR. For each item, read the relevant source files, check the box, and note any finding.

Invoke

Using the Extract Facade from Base/Lib skill (review mode), audit the extraction
of Git::Base#<method_name>.

R1 — Source analysis

• Pattern identified. Confirm which source pattern (A, B, or C) applies by reading Git::Base and Git::Lib.
• Signature preserved. The facade method's signature (positional args, optional args, keyword splat) matches the 4.x Git::Base#<method> signature exactly.
• Return type correct. The facade returns the same type as the legacy implementation (e.g. String from .stdout, not CommandLineResult). Read the source — do not rely on YARD tags alone.
• 4.x options only in allowlist. The *_ALLOWED_OPTS constant contains only keys declared in the corresponding *_OPTION_MAP in 4.x/lib/git/lib.rb. Look up the map at https://github.com/ruby-git/ruby-git/blob/4.x/lib/git/lib.rb. Any extra keys are a finding.
• Pre-processing ported. All option whitelisting, deprecation handling, and key normalization from Git::Lib is reproduced in the facade. Nothing was left behind in Git::Lib.
• Post-processing ported. Any parsing or result-class assembly that lived in Git::Lib is reproduced in the facade.

R2 — Legacy test coverage

• Legacy tests exist and pass. tests/units/ has tests exercising the public method. Verify with bundle exec bin/test <test-file-basename>.
• All 4.x options exercised. Every option in *_ALLOWED_OPTS has at least one legacy or integration test that passes an actual value and asserts the outcome.

R3 — Command class

• Command class exists. The Git::Commands::* class used by the facade exists in lib/git/commands/.
• Arguments DSL covers the allowlisted options. Every key in *_ALLOWED_OPTS maps to a declared entry in the command's arguments block.

R4 — Facade implementation

• Topic module correct. The facade method is placed in the right Git::Repository::* module per the redesign topic groupings.
• assert_valid_opts! used. The facade calls Git::Repository::Internal.assert_valid_opts!(ALLOWED_OPTS, **) before forwarding to the command.
• *_ALLOWED_OPTS placement correct. Each <METHOD>_ALLOWED_OPTS constant is declared immediately before the public facade method that uses it (not grouped at the top of the module, not inside Private).
• YARD docs complete. Each allowed option has an @option tag with type, name, default, and description. @param, @return, @raise are present and accurate.
• Unit specs present. spec/unit/git/repository/<topic>_spec.rb covers: default call, explicit path(s), each documented option, unknown option raises ArgumentError, return value is .stdout.
• Integration specs present (or explicitly skipped). Write spec/integration/git/repository/<topic>_spec.rb only when the facade adds behavior not exercised by any single command's integration tests — specifically multi-command orchestration or facade-owned post-processing of real git output. For one-line delegators (e.g. #add, #reset) the command's own integration tests already provide end-to-end coverage; omit the facade integration spec and add a comment in the unit spec explaining which command integration specs provide coverage.

R5 — Delegation

• Git::Base delegates. The original Git::Base method is a one-line forward to facade_repository.<method>(...).
• Git::Lib delegates (Pattern A/B only). The original Git::Lib method is a one-line forward to the facade.
• Legacy tests still pass after delegation. Run bundle exec bin/test <test-file-basename> against the delegating methods.

R6 — Quality gates

• bundle exec rspec passes
• bundle exec rubocop passes
• bundle exec rake yard passes (no undocumented public methods)