test(ci): add changelog job that runs cargo xtask changelog

Author: ErichDonGubler

.github/workflows/ci.yml

@@ -766,3 +766,62 @@ jobs:
           arguments: --all-features --workspace
           command-arguments: -Dwarnings -Aunmatched-organization
           rust-version: ${{ env.REPO_MSRV }}
+
+  changelog:
+    timeout-minutes: 2
+
+    name: Check `CHANGELOG` for errors
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v5
+
+      - uses: actions/github-script@v7
+        id: get-pull
+        with:
+          script: |
+            let pr = (await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number
+            })).data
+
+            let is_fork = pr.head.repo.fork && (pr.base.repo.clone_url !== pr.head.repo.clone_url)
+
+            if (is_fork) {
+              let head_repo = await github.rest.repos.get({
+                owner: pr.head.repo.owner.login,
+                repo: pr.head.repo.name
+              })
+              head_repo = head_repo.data
+              pr.base.repo.clone_url = head_repo.parent.clone_url
+            }
+
+            let pull = {
+              is_fork,
+              base_git: pr.base.repo.clone_url,
+            }
+
+            console.log(pull)
+            return pull
+
+      - name: Get base branch
+        shell: bash
+        run: |
+          REMOTE=origin
+          if ${{ fromJSON(steps.get-pull.outputs.result).is_fork }}; then
+            git remote add upstream ${{ fromJSON(steps.get-pull.outputs.result).base_git }}
+            git fetch upstream
+            REMOTE=upstream
+          fi
+          git branch -f ${{ github.base_ref }} $REMOTE/${{ github.base_ref }}
+
+      - name: Caching
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: clippy-${{ matrix.target }}-${{ matrix.kind }}-${{ env.CACHE_SUFFIX }}
+
+      - name: Run `cargo xtask changelog …`
+        run: |
+          cargo xtask changelog "${{ github.base_ref }}"