Copilot CLI - adopt new git extension API to improve applying a patch

[lszomoru]

Fixes microsoft/vscode#286066

[Copilot]

Pull request overview

This PR adopts a new Git extension API (diffBetweenPatch) to improve the process of applying patches from worktrees. The change simplifies the existing code by replacing a multi-step approach (getting diff stats then fetching individual patches) with a single API call that returns the complete patch directly.

Key changes:

• Adds diffBetweenPatch method to the Git extension API type definitions
• Updates IGitService interface and all implementations to make the path parameter optional
• Refactors applyWorktreeChanges to use the new API, eliminating the need for multiple diff calls and array coalescing

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/platform/git/vscode/git.d.ts	Adds diffBetweenPatch method signature to Repository interface
src/platform/git/common/gitService.ts	Updates IGitService interface to make path parameter optional in diffBetweenPatch
src/platform/git/vscode/gitServiceImpl.ts	Updates implementation to call the new diffBetweenPatch API method (previously incorrectly called diffBetween)
src/platform/test/node/simulationWorkspaceServices.ts	Updates test mock to match new signature with optional path parameter
src/platform/ignore/node/test/mockGitService.ts	Updates mock implementation to match new signature with optional path parameter
src/extension/chatSessions/vscode-node/chatSessionWorktreeServiceImpl.ts	Simplifies patch generation by using single diffBetweenPatch call instead of multiple calls; removes unused coalesce import