Run the changelog PR reference check in CI

Add a mise task for the script and run it in the lint job of pull
requests, fetching the full history so that the script can find the
merge base and the branches the pull request merged in.

#1236

Changelog: none
Assisted-by: Claude Code:claude-opus-5-5

Author: co2plant

.github/workflows/main.yaml

@@ -253,8 +253,19 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v6
+      with:
+        # '0' as a string: the number 0 is falsy in expressions
+        fetch-depth: ${{ github.event_name == 'pull_request' && '0' || '1' }}
     - uses: ./.github/actions/setup-mise
     - run: mise run check
+    - if: github.event_name == 'pull_request' && github.repository == 'fedify-dev/fedify'
+      env:
+        PR_NUMBER: ${{ github.event.pull_request.number }}
+        BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+      run: >-
+        mise run --skip-deps check:changelog-pr-refs --
+        --pr "$PR_NUMBER" --base "$BASE_SHA" --head "$HEAD_SHA"
 
   release-test:
     runs-on: ubuntu-latest

mise.toml

@@ -230,6 +230,10 @@ deno run --allow-read --allow-write scripts/check_versions.ts ...$fix_args ...$s
 description = "Ensure @fedify/fixture is only used in **/*.test.ts files"
 run = "deno run --allow-read scripts/check_fixture_usage.ts"
 
+[tasks."check:changelog-pr-refs"]
+description = "Check that changelog entries added by a pull request reference it"
+run = "deno run --allow-read --allow-run=git scripts/check_changelog_pr_refs.ts"
+
 [tasks."check:workspace-protocol"]
 description = "Check for invalid workspace: specifiers without version (*, ^, ~)"
 run = "deno run --allow-read scripts/check_workspace_protocol.ts"