PROTOTYPE: feat(init): git init features

[bepri]

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A prototype to add Git features to the init command.

CRAFT-5060

[Copilot]

Pull request overview

This PR prototypes VCS (Git) support for the init command by adding a --vcs flag, initializing a Git repository during project initialization, and extending Testcraft to customize generated .gitignore entries.

Changes:

• Add --vcs {git,none} to craft_application’s init command and run VCS setup during initialization.
• Rename GitRepo._init_repo() to GitRepo.init_repo() and update unit tests accordingly.
• Add Testcraft InitCommand override plus unit/spread tests covering VCS behavior.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/unit/services/test_remotebuild.py	Updates mocks/assertions for the init_repo rename.
tests/unit/git/test_git.py	Updates patch targets from _init_repo to init_repo.
tests/unit/commands/test_init.py	Adds vcs arg coverage and new tests for VCS initialization and .gitignore creation.
tests/spread/testcraft/init-vcs/task.yaml	Adds spread test coverage for Testcraft init with/without VCS.
testcraft/commands/init.py	Introduces Testcraft-specific InitCommand overriding vcs_ignore_globs.
testcraft/commands/init.py	Exports the new InitCommand.
testcraft/cli.py	Registers Testcraft InitCommand (overriding default init).
craft_application/git/_git_repo.py	Renames repository initialization method to init_repo.
craft_application/commands/init.py	Implements --vcs flag, VCS initialization, and .gitignore appending logic.

[bepri]

The intention here was to create an easy way to customize what entries appear in a generated gitignore. For example, if Snapcraft overrides this to return ["*.snap", "*.comp"], it would add this to a gitignore file:

# Added by Snapcraft
*.snap
*.comp

[bepri]

This copies how uv handles it, which is certainly future-proof, but I'm considering doing --no-vcs as an opt-out flag and removing --vcs as a flag since I doubt we'll support anything other than git any time soon.