bundle: fix performance regression when bundling file changes (issue4031) Somewhere before 2.7, a change [ec896f9e8894] was committed that entailed a large performance regression when bundling (and therefore remote cloning) repositories. For each file in the repository, it would recompute the set of needed changesets even though it is the same for all files. This computation would dominate bundle runtimes according to profiler output (by 10x or more).