Move transaction::Version to primitives

We would like to move the `Transaction` type to `primitives`, as a step
towards this move the `transaction::Version` and its trait imps (just
`Display`) over there.

bitcoin/src/blockdata/transaction.rs

@@ -31,6 +31,10 @@ use crate::sighash::{EcdsaSighashType, TapSighashType};
 use crate::witness::Witness;
 use crate::{Amount, FeeRate, SignedAmount, VarInt};
 
+#[rustfmt::skip]            // Keep public re-exports separate.
+#[doc(inline)]
+pub use primitives::transaction::*;
+
 hashes::hash_newtype! {
     /// A bitcoin transaction hash/transaction ID.
     ///
@@ -925,27 +929,6 @@ impl std::error::Error for IndexOutOfBoundsError {
     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { None }
 }
 
-/// The transaction version.
-///
-/// Currently, as specified by [BIP-68], only version 1 and 2 are considered standard.
-///
-/// Standardness of the inner `i32` is not an invariant because you are free to create transactions
-/// of any version, transactions with non-standard version numbers will not be relayed by the
-/// Bitcoin network.
-///
-/// [BIP-68]: https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki
-#[derive(Copy, PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct Version(pub i32);
-
-impl Version {
-    /// The original Bitcoin transaction version (pre-BIP-68).
-    pub const ONE: Self = Self(1);
-
-    /// The second Bitcoin transaction version (post-BIP-68).
-    pub const TWO: Self = Self(2);
-}
-
 crate::internal_macros::define_extension_trait! {
     /// Extension functionality for the [`Version`] type.
     pub trait VersionExt impl for Version {
@@ -969,10 +952,6 @@ impl Decodable for Version {
     }
 }
 
-impl fmt::Display for Version {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { fmt::Display::fmt(&self.0, f) }
-}
-
 impl_consensus_encoding!(TxOut, value, script_pubkey);
 
 impl Encodable for OutPoint {

primitives/src/lib.rs

@@ -33,6 +33,7 @@ pub mod locktime;
 pub mod opcodes;
 pub mod pow;
 pub mod sequence;
+pub mod transaction;
 
 #[doc(inline)]
 pub use units::*;

primitives/src/transaction.rs

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: CC0-1.0
+
+//! Bitcoin transactions.
+//!
+//! A transaction describes a transfer of money. It consumes previously-unspent
+//! transaction outputs and produces new ones, satisfying the condition to spend
+//! the old outputs (typically a digital signature with a specific key must be
+//! provided) and defining the condition to spend the new ones. The use of digital
+//! signatures ensures that coins cannot be spent by unauthorized parties.
+//!
+//! This module provides the structures and functions needed to support transactions.
+
+use core::fmt;
+
+/// The transaction version.
+///
+/// Currently, as specified by [BIP-68], only version 1 and 2 are considered standard.
+///
+/// Standardness of the inner `i32` is not an invariant because you are free to create transactions
+/// of any version, transactions with non-standard version numbers will not be relayed by the
+/// Bitcoin network.
+///
+/// [BIP-68]: https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki
+#[derive(Copy, PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct Version(pub i32);
+
+impl Version {
+    /// The original Bitcoin transaction version (pre-BIP-68).
+    pub const ONE: Self = Self(1);
+
+    /// The second Bitcoin transaction version (post-BIP-68).
+    pub const TWO: Self = Self(2);
+}
+
+impl fmt::Display for Version {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { fmt::Display::fmt(&self.0, f) }
+}