Merge rust-bitcoin#2196: Backport rust-bitcoin#1820 and bump minor version 0.30.2

ba99aa4 Bump version to 0.30.2 (Tobin C. Harding)
3c9bbca Expose valid (min, max) difficulty transition thresholds (Wilmer Paulino)

Pull request description:

  Patch one backports rust-bitcoin#1820, I believe this is all that is needed for LDK to be able to upgrade to `rust-bitcoin v0.30`.

  Context:

  - rust-bitcoin#1820
  - lightningdevkit/rust-lightning#2124

  Patch 2 adds a changelog entry and bumps the minor version.

ACKs for top commit:
  Kixunil:
    ACK ba99aa4

Tree-SHA512: 93adb52bbc8e61ece63e5653dea7cf6d2d25028f25cb8bbda14606d9ebf74becaee0a0c4f4f3d7fde56c0e2b8a57f8c9be263e04833161a1da0baaf8fcca8764

Author: apoelstra

bitcoin/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.30.2 - 2023-11-16
+
+- Expose valid (min, max) difficulty transition thresholds [#1820](Expose valid (min, max) difficulty transition thresholds)
+
 # 0.30.1 - 2023-07-16
 
 - Fix compilation when [`RUSTFLAGS=--cfg=bench` is set](https://github.com/rust-bitcoin/rust-bitcoin/pull/1943)

bitcoin/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bitcoin"
-version = "0.30.1"
+version = "0.30.2"
 authors = ["Andrew Poelstra <[email protected]>"]
 license = "CC0-1.0"
 repository = "https://github.com/rust-bitcoin/rust-bitcoin/"

bitcoin/src/pow.rs

@@ -235,6 +235,20 @@ impl Target {
     /// [`difficulty`]: Target::difficulty
     #[cfg_attr(all(test, mutate), mutate)]
     pub fn difficulty_float(&self) -> f64 { TARGET_MAX_F64 / self.0.to_f64() }
+
+    /// Computes the minimum valid [`Target`] threshold allowed for a block in which a difficulty
+    /// adjustment occurs.
+    ///
+    /// The difficulty can only decrease or increase by a factor of 4 max on each difficulty
+    /// adjustment period.
+    pub fn min_difficulty_transition_threshold(&self) -> Self { Self(self.0 >> 2) }
+
+    /// Computes the maximum valid [`Target`] threshold allowed for a block in which a difficulty
+    /// adjustment occurs.
+    ///
+    /// The difficulty can only decrease or increase by a factor of 4 max on each difficulty
+    /// adjustment period.
+    pub fn max_difficulty_transition_threshold(&self) -> Self { Self(self.0 << 2) }
 }
 do_impl!(Target);