Fix wrong file list when creating PR (#8468)

* Initial plan

* Initial analysis of wrong file list issue in PR creation

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Fix wrong file list when creating PR by initializing _compareBranch correctly

The constructor was incorrectly initializing _compareBranch to baseBranch
instead of the actual compareBranch parameter. This caused the file diff
comparison to potentially use wrong branches before setCompareBranch completed
its async initialization, resulting in displaying the wrong list of files
when creating a PR.

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Revert proposed changes

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/view/createPullRequestDataModel.ts

@@ -45,7 +45,7 @@ export class CreatePullRequestDataModel extends Disposable {
 		super();
 		this._baseOwner = baseOwner;
 		this._baseBranch = baseBranch;
-		this._compareBranch = baseBranch;
+		this._compareBranch = compareBranch;
 		this._gitcontentProvider = new GitContentProvider(this.folderRepositoryManager);
 		this._compareGitHubRepository = this.folderRepositoryManager.gitHubRepositories.find(githubRepo => githubRepo.remote.owner === compareOwner && githubRepo.remote.repositoryName === repositoryName);
 		this._gitHubcontentProvider = new GitHubContentProvider(this.folderRepositoryManager.gitHubRepositories);