deltas: skip if projected compressed size is bigger than previous snapshot If we have a delta, we check constraints against a lower bound estimate of the resulting compressed delta. We then checks this projected size against the `size(snapshotⁿ) > size(snapshotⁿ⁺¹)` constraint. This allows to exclude potential base candidates before doing any expensive computation. This only apply to the intermediate-snapshot case since this constraint only apply to them. For some pathological cases of a private repository this step provide a further performance boost (timing from `hg perfrevlogwrite`): before: 3.010646 seconds after: 2.609307 seconds