feat: Add build-time policy to disable self-update in packaged builds

[melund]

Description

Add a build-time self-update policy so package-manager distributions of apm (for example pixi or brew) can disable apm update and show a custom guidance message instead.

This is useful for for example the conda-forge packaged version of apm, which I have added here:
https://github.com/conda-forge/apm-cli-feedstock

In such cases apm should not update it self.

The PR creates a update_policy module which package mangers can patch. It wires the policy into the update command and startup update notification path.

The PR also updates docs to explain distribution-managed update behavior. It also adds unit tests for the new disabled-policy flow.

Type of change

• Bug fix
• New feature
• Documentation
• Maintenance / refactor

Testing

• Tested locally
• All existing tests pass
• Added tests for new functionality (if applicable)

[Copilot]

Pull request overview

Adds a build-time policy hook that allows packaged/distribution builds (brew/pixi/conda, etc.) to disable apm update and provide distributor-specific update guidance, while also adjusting the startup update notification behavior.

Changes:

• Introduces src/apm_cli/update_policy.py with patchable constants and helper accessors for self-update enablement and messaging.
• Wires the policy into apm update (early exit with guidance) and into _check_and_notify_updates() (skip update notifications when disabled).
• Updates CLI reference docs and adds unit tests covering the disabled-policy flows.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/unit/test_update_command.py	Adds a unit test ensuring apm update exits successfully and skips network/installer when policy disables self-update.
tests/unit/test_command_helpers.py	Adds a unit test ensuring startup update checks are skipped when self-update is disabled.
src/apm_cli/update_policy.py	New centralized module for build-time self-update policy + guidance message helpers.
src/apm_cli/commands/update.py	Enforces the policy in the update command by short-circuiting when disabled.
src/apm_cli/commands/_helpers.py	Skips update notifications when disabled; uses a helper to render the update hint consistently.
docs/src/content/docs/reference/cli-commands.md	Documents distribution-managed update behavior and the skipped startup notification behavior.

[melund]

@microsoft-github-policy-service agree

[sergio-sisternes-epam]

Thanks for the contribution @melund -- great use case for conda-forge and other distribution-managed builds. The overall design is clean and well-scoped.

One change requested: the bool() coercion on SELF_UPDATE_ENABLED can silently defeat the policy when packagers use string substitution during builds. See the inline comment for a one-line fix using identity check (is True) that fails safe.

[melund]

Do you want me to rebase, or can you just squash-merge the PR?