This allows the signer to know the signing context precisely without
relying on heuristics on the psbt fields.
Due to the context being static, we still have to look at the PSBT when
producing taproot signatures to determine the set of leaf hashes that
the key can sign for.
Idiomatic Rust uses lowercase for acronyms for all characters after the
first e.g. `std::net::TcpStream`. PSBT (Partially Signed Bitcoin
Transaction) should be rendered `Psbt` in Rust code if we want to write
idiomatic Rust.
Use `Psbt` instead of `PSBT` when aliasing the import of
`PartiallySignedTransaction` from `bitcoin` library.
While technically it's not required since there are no timelocks inside,
it's still less confusing for the end user if we allow this instead of
failing like we do currently.
The `TooManyItemsSelected` error has been removed, since it's not technically an
error but potentailly more of an "over-constraint" over a tx: for instance,
given a `thresh(3,pk(a),pk(b),older(10),older(20))` descriptor one could create
a spending tx with the `[0,1,2]` items that would only be spendable after `10`
blocks, or a tx with the `[0,2,3]` items that would be spendable after `20`.
In this case specifying more items than the threshold would create a tx with
the maximum constraint possible, in this case the `20` blocks. This is not
necessarily an error, so we should allow it without failing.
Change the return type of the `descriptor!()` macro and `ToWalletDescriptor` to
avoid having to map errors.
Also introduce more checks to validate descriptors built using the macro.
The syntax now is pretty much the same as the normal descriptor syntax,
with the only difference that modifiers cannot be grouped together (i.e.
`sdv:older(144)` must be turned into `s:d:v:older(144)`.
This commit also fixes the timelock comparing logic in the policy module, since
the rules are different for absolute (OP_CLTV) and relative (OP_CSV) timelocks.
Fixes#215
This allows specifying different "policy paths" for the internal and external
descriptors, and adds additional checks to make sure they are compatibile (i.e.
the timelocks are expressed in the same unit).
It's still suboptimal, since the `n_sequence`s are per-input and not per-transaction,
so it should be possibile to spend different inputs with different, otherwise
incompatible, `CSV` timelocks, but that requires a larger refactor that
can be done in a future patch.
This commit also tries to clarify how the "policy path" should be used by adding
a fairly detailed example to the docs.
