An even fancier CHANGELOG check in CI (#8416)

.github/workflows/changelog.yml

@@ -6,6 +6,12 @@ on:
       - ".github/workflows/changelog.yml"
       - "CHANGELOG.md"
       - "xtask/**/*"
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - labeled
+      - unlabeled
 
 env:
   #
@@ -38,6 +44,7 @@ jobs:
         with:
           fetch-depth: 0
 
+      # NOTE: Keep label name(s) in sync. with `xtask`'s implementation.
       - name: Run `cargo xtask changelog …`
         run: |
-          cargo xtask changelog "origin/${{ github.event.pull_request.base.ref }}"
+          cargo xtask changelog "origin/${{ github.event.pull_request.base.ref }}" ${{ contains(github.event.pull_request.labels.*.name, 'changelog: released entry changed') && '--allow-released-changes' || ''  }}

xtask/src/changelog.rs

@@ -6,6 +6,7 @@ use xshell::Shell;
 
 pub(crate) fn check_changelog(shell: Shell, mut args: Arguments) -> anyhow::Result<()> {
     const CHANGELOG_PATH_RELATIVE: &str = "./CHANGELOG.md";
+    let allow_released_changes = args.contains("--allow-released-changes");
 
     let from_branch = args
         .free_from_str()
@@ -72,7 +73,12 @@ pub(crate) fn check_changelog(shell: Shell, mut args: Arguments) -> anyhow::Resu
             "one or more checks against `{}` failed; see above for details",
             CHANGELOG_PATH_RELATIVE,
         );
-        Err(anyhow::Error::msg(msg))
+        if allow_released_changes {
+            log::warn!("{msg}");
+            Ok(())
+        } else {
+            Err(anyhow::Error::msg(msg))
+        }
     } else {
         Ok(())
     }

xtask/src/main.rs

@@ -53,6 +53,8 @@ Commands:
 
         `<to_commit>` is the tip of the `git diff` that will be used for checking (1).
 
+    --allow-released-changes  Only reports issues as warnings, rather than reporting errors and forcing a non-zero exit code.
+
   miri
     Run all miri-compatible tests under miri. Requires a nightly toolchain
     with the x86_64-unknown-linux-gnu target and miri component installed.