Add `/upgrade` command to Copilot CLI

[chrisreddington]

Describe the feature or problem you'd like to solve

Currently, it's unclear if there's a way to check for or install Copilot CLI updates from within the CLI itself. Users must remember to manually update via their package manager or re-run the install script.

Proposed solution

Add an /upgrade command that:

1. Checks if a newer version is available by comparing current version against latest release
2. Displays the current version vs. latest version with changelog highlights
3. Installs the update (or provides instructions based on install method)

Example Usage

# Check for updates and upgrade if available
copilot
> /upgrade

# Output example:
# Current version: v0.0.389
# Latest version:  v0.0.392
# 
# Changelog highlights:
# - One new feature
# - Two new feature
# - Three new feature
#
# Update available! Upgrading...
# ✓ GitHub Copilot CLI updated to v0.0.392

Example prompts or workflows

No response

Additional context

Optional Enhancements

1. Startup Notification

Add a --check-for-updates startup flag that notifies users when a new version is available (non-blocking):

copilot --check-for-updates

# Output if outdated:
# ℹ A new version is available (v0.0.395). Run /upgrade to update.

2. Auto-Update Preference

Add a config option to automatically check for updates on startup:

# In ~/.copilot/config
{
  "check_for_updates_on_startup": true
}

If this does already exist (implied by the CHANGELOG), then would be great to have this documented more clearly.

[hubwriter]

➕ This would be great.

[williammartin]

Copilot CLI currently updates itself on startup, and it is toggleable in config with auto_update: true (default) or auto_update: false, documented in copilot help config, or toggle off with --no-auto-update, documented in copilot --help.

Still, there's probably something better we can do to convey this, since you didn't notice it. Any thoughts?

[williammartin]

When the CLI updates itself a message is dropped into the timeline. We've also discussed getting changelog items in there, which would probably increase the visibility.