Coin selection requires knowing the weight of a transaction so that fees
can be estimated. However for external inputs, the weight may not be
avialble, and solving data may not be enough as the input could be one
that we do not support. By allowing users to specify input weights,
those external inputs can be included in the transaction.
Additionally, if the weight for an input is specified, that value will
always be used, regardless of whether the input is in the wallet or
solving data is available. This allows us to account for scenarios where
the wallet may be more conservative and estimate a larger input than may
actually be created.
For example, we assume the maximum DER signature size, but an external
input may be signed by a wallet which does nonce grinding in order to get
a smaller signature. In that case, the user can specify the smaller
input weight to avoid overpaying transaction fees.
c0405ee27f rpc: Document that DEFAULT is for Taproot, ALL for everything else (Andrew Chow)
d3992669df psbt: Actually use SIGHASH_DEFAULT (Andrew Chow)
eb9a1a2c59 psbt: Make sighash_type std::optional<int> (Andrew Chow)
Pull request description:
Make the behavior align with the help text by actually using SIGHASH_DEFAULT as the default sighash for signing PSBTs.
ACKs for top commit:
Sjors:
re-utACK c0405ee27f
Tree-SHA512: 5199fb41de416b2f10ac451f824e7c94b428ba11fdb9e50f0027c692e959ce5813a340c34a4e52d7aa128e12008303d80939a693eff36a869720e45442119828
