extensions/git/src/git.ts/Repository/findTrackingBranches
class Repository:	async findTrackingBranches(upstreamBranch: string): Promise<Branch[]> {
		const result = await this.exec(['for-each-ref', '--format', '%(refname:short)%00%(upstream:short)', 'refs/heads']);
		return result.stdout.trim().split('\n')
			.map(line => line.trim().split('\0'))
			.filter(([_, upstream]) => upstream === upstreamBranch)
			.map(([ref]) => ({ name: ref, type: RefType.Head } as Branch));
	}