Restore PR extension management with API-first approach

[Copilot]

Restores logic from commit 1cafcac that was removed, polishing it to align with the GitHub API-first pattern established in commit 361cb48.

Changes

Restored extension management infrastructure:

• isPullRequestExtensionInstalled() - checks extension availability
• installPullRequestExtension() - auto-installs extension with prerelease detection for Insiders builds
• Context key updates for prExtensionInstalledContextKey

Command routing strategy:

• checkoutFromDescription and applyChangesFromDescription - proxy commands that install PR extension on-demand (requires extension functionality)
• closeChatSessionPullRequest - uses GitHub API directly (no extension required)

UI Integration:

• Added menu contributions in chat/chatSessions for checkout and apply changes commands
• Commands appear in copilot-cloud-agent chat sessions when PR extension is not installed
• Uses context key !github.copilot.prExtensionInstalled to conditionally show menu items
• Includes localized titles and appropriate icons (desktop-download, diff)

Improvements:

• Added JSDoc documentation
• Enhanced error logging with operation context
• Early return optimization in polling loop
• Info-level logging for installation flow

Example

// Commands requiring PR extension features auto-install it
vscode.commands.registerCommand('github.copilot.cloud.sessions.proxy.checkoutFromDescription', async (ctx) => {
    await this.installPullRequestExtension();  // Ensures extension availability
    await vscode.commands.executeCommand('pr.checkoutFromDescription', ctx?.path);
});

// Commands with API equivalents bypass extension
vscode.commands.registerCommand(CLOSE_SESSION_PR_CMD, async (ctx) => {
    await this.octoKitService.closePullRequest(owner, repo, number);  // Direct API call
});

User Experience

When viewing copilot-cloud-agent chat sessions without the GitHub Pull Request extension installed, users will see:

• Checkout Pull Request button - installs extension and checks out the PR branch
• Apply Changes from Pull Request button - installs extension and applies PR changes

These buttons automatically disappear once the PR extension is installed, providing a seamless onboarding experience.

Created from VS Code via the GitHub Pull Request extension.

Original prompt

Restore the logic in this commit 1cafcac and polish it

Created from VS Code via the GitHub Pull Request extension.

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[joshspicer]

@copilot you need to actually show the button to install the extension in the chat part, eg:

contributes.menu
"chat/multiDiff/context": [
{
"command": "xxxxx"
},
{

---

[Copilot]

@copilot you need to actually show the button to install the extension in the chat part, eg:

contributes.menu...

Added UI menu contributions in commit f2f7859.

The commands now appear in the chat sessions context menu for copilot-cloud-agent sessions:

• "Checkout Pull Request" (icon: desktop-download)
• "Apply Changes from Pull Request" (icon: diff)

Both commands use the context key !github.copilot.prExtensionInstalled to only show when the PR extension is not installed. When clicked, they automatically install the GitHub Pull Request extension and execute the corresponding command.

The menu items are in the chat/chatSessions contribution point with group prExtension@1 and prExtension@2, similar to how the existing "Close Pull Request" command appears in the context group.