Skip Inno spawn when another instance is already installing

[dmitrivMS]

Fixes #62476

Problem

When two VS Code Insiders instances are running against the same install (for example a normal instance plus one started with --transient) and an update becomes available, both instances independently progress through the update state machine to doApplyUpdate for the same downloaded CodeSetup-*.exe and each spawn Inno Setup.

The second spawn races into Inno's built-in "Setup is already running" modal, because Inno protects itself with a global per-install mutex.

Fix

In updateService.win32.ts doApplyUpdate, check the existing ${win32MutexName}-updating Windows named mutex (already held by the running Inno Setup process) before spawning. If another instance is already running setup for this install:

• Skip the spawn.
• Do not track an updateProcess (we must not kill the other instance's installer if the user cancels here).
• Keep the existing -ready mutex polling loop running so this instance still transitions Updating → Ready when the other instance's install finishes.

The existing 1-hour cancelTimeout continues to act as the safety net if the other instance crashes mid-install.

Notes

• All filesystem coordination (flag file, cancel file, progress file, cache path) is already shared between instances, so the non-spawning instance still observes the same install correctly.
• A tiny residual race remains (both isActive checks return false before either process actually grabs the mutex), but the reported scenario — one instance already mid-install when the other tries to start — is handled.
• No new dependency: reuses @vscode/windows-mutex already imported a few lines down for -ready.

[Copilot]

Pull request overview

Prevents multiple VS Code instances sharing the same Windows installation from spawning a second Inno Setup installer during a background update, avoiding Inno’s “Setup is already running” modal by checking the existing *-updating named mutex before spawning.

Changes:

• Adds an -updating mutex pre-check in doApplyUpdate to detect an already-running installer.
• Skips spawning and process tracking when another instance is already installing, relying on existing -ready mutex polling to advance state.
• Logs when installation is delegated to another instance.

Show a summary per file

File	Description
src/vs/platform/update/electron-main/updateService.win32.ts	Adds -updating mutex check to avoid spawning a second Inno Setup installer and continues readiness polling.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 2

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1