Merge pull request rust-bitcoin#25 from tcharding/12-06-fmt-in-ci

CI: Run the formatter

Author: tcharding

.github/workflows/README.md

@@ -0,0 +1,28 @@
+# corepc workflow notes
+
+Because there are so many integration test jobs (one for each version
+of Core supported) we cannot stay under the 20 job limit.
+
+ref: https://docs.github.com/en/actions/learn-github-actions/usage-limits-billing-and-administration
+
+The minimal/recent lock files are handled by CI (`rust.yml`).
+
+## Jobs
+
+Run from `rust.yml` unless stated otherwise. Total 11 jobs.
+
+0.  `Prepare`
+1.  `Stable - minimal`
+2.  `Stable - recent`
+3.  `Nightly - minimal`
+4.  `Nightly - recent`
+5.  `MSRV - minimal`
+6.  `MSRV - recent`
+7.  `Lint`
+8.  `Docs`
+9.  `Docsrs`
+10. `Format`
+
++1 job for each supported version of Core.
+
+

.github/workflows/rust.yaml

@@ -170,6 +170,24 @@ jobs:
       - name: "Run test script"
         run: ./maintainer-tools/ci/run_task.sh docsrs
 
+  Format:                       #  1 job, run cargo fmt directly.
+    name: Format - nightly toolchain
+    needs: Prepare
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    steps:
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Select toolchain"
+        uses: dtolnay/rust-toolchain@v1
+        with:
+          toolchain: ${{ needs.Prepare.outputs.nightly_version }}
+      - name: "Install rustfmt"
+        run: rustup component add rustfmt
+      - name: "Check formatting"
+        run: cargo fmt --all -- --check
+
   Integration:                  # 1 job for each bitcoind version we support.
     name: Integration tests - stable toolchain
     runs-on: ubuntu-latest