This pull request is identical to recently closed#19, but applied to the current head. I think #19 may have been closed erroneously. If MEM takes as an input a set of elements of type 'elt, then if it also takes another input which is an element to test for membership, clearly that other input must be of type 'elt.
If #19 was not closed erroneously, then please explain, and i will stop reopening this issue.
Operations now include a block hash in their header. Such an operation
could only be included in a successor of this block.
Furthermore, when validating a block, the economic protocol now
returns---together with the context---an integer `max_operations_ttl`.
Then, when validating a successor, the shell will fail if it contains
an operation whose header's block hash is not one the
`max_operations_ttl` predecessors of the block.
As a bonus, the shell is now able to detect and forbid replayed
operations. Then, we might decide to remove some replay
detection-mechanism that we previously implemented in the economic
protocol.
It now takes a `proto_header` in parameter, and it returns a full
`shell_header`. This prepares the inclusion of the context's hash in the
`shell_header`.
The `begin_construction` function now accepts an optional argument
`proto_header`. This is to be used by a new RPC that ease forging the
shell header of a block (i.e. it will compute the fitness and, in a
near future, the hash of the resulting context).
This prepares the context to the inclusion the hash of the context in
the block header. By "looking" into the resulting context of a block,
we are now know able to determine whether:
- no testnet is currently associated to the branch;
- a testnet must be forked after the block;
- a previously forked testnet is running.
