addrevision: use general delta when the incoming base delta is bad We unify the delta selection process to be a simple three options process: - try to use the incoming delta (if lazydeltabase is on) - try to find a suitable parents to delta against (if gd is on) - try to delta against the tipmost revision The first of this option that yield a valid delta will be used. The test change in 'test-generaldelta.t' show this behavior as we use a delta against the parent instead of a full delta when the incoming delta is not suitable. This as some impact on 'test-bundle.t' because a delta somewhere changes. It does not seems to change the test semantic and have been ignored.

test: use a bigger manifest in general delta test The currently used manifest is too small and cannot sustain a chain length above "1". This make testing the 'lazybasedelta' behavior hard. So we add an extra file in the manifest to help testing in the next changeset. The semantic of existing tests have been checked and is not changed.

addrevision: rework generaldelta computation The old code have multiple explicit tests and code duplications. This makes it hard to improve the code. We rewrite the logic in a more generic way, not changing anything of the computed result. The final goal here is to eventually be able to: - factor out the default fallback case "try against 'prev'" in a single place - allow 'lazydeltabase' case to use the smarter general delta code path when the incoming base does not provide us with a good delta.