Apply suggestions from code review

Co-authored-by: Daira Hopwood <daira@jacaranda.org>

zcash_extensions/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "zcash_extensions"
-description = "TBD"
+description = "Zcash Extension implementations & consensus node integration layer."
 version = "0.0.0"
 authors = ["Jack Grigg <jack@z.cash>", "Kris Nuttycombe <kris@z.cash>"]
 homepage = "https://github.com/zcash/librustzcash"

zcash_primitives/src/extensions/transparent.rs

@@ -10,7 +10,7 @@ use std::fmt;
 pub trait FromPayload: Sized {
     type Error;
 
-    /// Parses an extension type from a mode and payload.
+    /// Parses an extension-specific witness or precondition from a mode and payload.
     fn from_payload(mode: u32, payload: &[u8]) -> Result<Self, Self::Error>;
 }
 

zcash_primitives/src/transaction/builder.rs

@@ -201,9 +201,9 @@ impl TransparentInputs {
             return Err(Error::InvalidAmount);
         }
 
-        // ensure that the ripemd160 digest of the public key associated with the
+        // Ensure that the RIPEMD-160 digest of the public key associated with the
         // provided secret key matches that of the address to which the provided
-        // output may be spent
+        // output may be spent.
         let pubkey = secp256k1::PublicKey::from_secret_key(&self.secp, &sk).serialize();
         match coin.script_pubkey.address() {
             Some(TransparentAddress::PublicKey(hash)) => {
@@ -756,7 +756,7 @@ impl<'a, P: consensus::Parameters, R: RngCore + CryptoRng> Builder<'a, P, R> {
         }
 
         //
-        // Signatures -- all effects must have been applied.
+        // Signatures -- everything but the signatures must already have been added.
         //
 
         let mut sighash = [0u8; 32];