build: new msrv job to isolate build tools

.github/workflows/ci.yml

@@ -11,11 +11,7 @@ jobs:
     strategy:
       matrix:
         platform: [ubuntu-latest, macos-latest, windows-latest]
-        # Minumum Supported Rust Version (MSRV) is 1.63.0.
-        toolchain: [1.63.0, stable, beta, nightly]
-        include:
-          - toolchain: 1.63.0
-            msrv: true
+        toolchain: [stable, beta, nightly]
     runs-on: ${{ matrix.platform }}
     steps:
       - uses: actions/checkout@v3
@@ -25,25 +21,40 @@ jobs:
           rustup component add --toolchain ${{ matrix.toolchain }} rustfmt
           rustup component add --toolchain ${{ matrix.toolchain }} clippy
           rustup update ${{ matrix.toolchain }}
-      # - name: Pin dependencies
-      #   if: matrix.msrv
-      #   run: cargo update -p allocator-api2 --precise "0.2.9" --verbose
       - name: Lint all targets
-        if: ${{ !matrix.msrv }}
         run: cargo clippy --all-targets
       - name: Format
-        if: ${{ !matrix.msrv }}
         run: cargo fmt -- --check
       - name: Build with defeault features
         run: cargo build --verbose
       - name: Check release build on Rust ${{ matrix.toolchain }}
         run: cargo check --release --verbose --color always
       - name: Unit test
-        if: ${{ !matrix.msrv }}
         run: cargo test --verbose --lib
       - name: Doc test
-        if: ${{ !matrix.msrv }}
         run: cargo test --verbose --doc
+  # Check that library code can be compiled with MSRV (1.63.0).
+  msrv:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      # Modify build tools just for MSRV testing. This avoids us having
+      # to bump our MSRV just for tooling. Tooling doesn't effect consumers so not a risk.
+      - name: Prepare environment for MSRV toolchain
+        run: |
+          # Remove resolver = "3" line for MSRV compatibility. We use V3 to
+          # generate an MSRV-compliant lockfile, but this isn't necessary to
+          # check if library code is MSRV compliant. Any resolver can go
+          # and grab the versions specified in the committed lockfile.
+          #
+          # The V3 resolver is standard in rust 1.85.
+          sed -i '/resolver = "3"/d' Cargo.toml
+      - name: Install MSRV toolchain
+        run: |
+          rustup toolchain install 1.63.0
+          rustup default 1.63.0
+      - name: Build with MSRV compiler
+        run: cargo build --verbose
   signet:
     runs-on: ubuntu-latest
     steps:

Cargo.toml

@@ -9,7 +9,8 @@ repository = "https://github.com/rustaceanrob/kyoto"
 readme = "README.md"
 keywords = ["bitcoin", "cryptography", "network", "peer-to-peer"]
 categories = ["cryptography::cryptocurrencies"]
-resolver = "2"
+# MSRV-aware resolver which is the default in edition2024.
+resolver = "3"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html