src/vs/workbench/contrib/scm/browser/scmViewPane.ts/RepositoryVisibilityActionController/onDidChangeVisibleRepositories
class RepositoryVisibilityActionController:	private onDidChangeVisibleRepositories(): void {
		let count = 0;

		for (const [repository, item] of this.items) {
			const isVisible = this.scmViewService.isVisible(repository);
			item.contextKey.set(isVisible);

			if (isVisible) {
				count++;
			}
		}

		this.repositoryCountContextKey.set(this.items.size);
		this.repositoryVisibilityCountContextKey.set(count);
	}