CI: Make BuggieBot reply to pull requests that fail the commit linter

This should help reduce the repeating "Please check the contributing
guide" replies from reviewers.

1 files changed, 54 insertions, 0 deletions

diff --git a/.github/workflows/lintcommits.yml b/.github/workflows/lintcommits.yml
new file mode 100644
index 0000000000..9e00ea67ae
--- /dev/null
+++ b/.github/workflows/lintcommits.yml
@@ -0,0 +1,54 @@
+name: Commit linter
+
+on: [pull_request_target]
+
+jobs:
+  lint_commits:
+    runs-on: ubuntu-20.04
+    if: always() && github.repository == 'SerenityOS/serenity'
+
+    steps:
+      - name: Get PR Commits
+        id: 'get-pr-commits'
+        uses: IdanHo/get-pr-commits@d94b66d146a31ef91e54a2597dee4fb523157232
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Check linebreaks
+        if: ${{ success() || failure() }}
+        uses: tim-actions/commit-message-checker-with-regex@v0.3.1
+        with:
+          commits: ${{ steps.get-pr-commits.outputs.commits }}
+          pattern: '^[^\r]*$'
+          error: 'Commit message contains CRLF line breaks (only unix-style LF linebreaks are allowed)'
+
+      - name: Check Line Length
+        uses: tim-actions/commit-message-checker-with-regex@v0.3.1
+        with:
+          commits: ${{ steps.get-pr-commits.outputs.commits }}
+          pattern: '^.{0,72}(\n.{0,72})*$'
+          error: 'Commit message lines are too long (maximum allowed is 72 characters)'
+
+      - name: Check subsystem
+        if: ${{ success() || failure() }}
+        uses: tim-actions/commit-message-checker-with-regex@v0.3.1
+        with:
+          commits: ${{ steps.get-pr-commits.outputs.commits }}
+          pattern: '^\S.*?: .+'
+          error: 'Missing category in commit title (if this is a fix up of a previous commit, it should be squashed)'
+
+      - name: Check title
+        if: ${{ success() || failure() }}
+        uses: tim-actions/commit-message-checker-with-regex@v0.3.1
+        with:
+          commits: ${{ steps.get-pr-commits.outputs.commits }}
+          pattern: '^.+[^.\n](\n.*)*$'
+          error: 'Commit title ends in a period'
+
+      - name: Comment on PR
+        if: ${{ failure() }}
+        uses: unsplash/comment-on-pr@85a56be792d927ac4bfa2f4326607d38e80e6e60
+        env:
+          GITHUB_TOKEN: ${{ secrets.BUGGIEBOT }}
+        with:
+          msg: "One or more of the commits in this PR do not match the [code submission policy](https://github.com/SerenityOS/serenity/blob/master/CONTRIBUTING.md#code-submission-policy), please check the `lint_commits` CI job for more details."