Split commit message checks into individual scripts

Split check-commit-messages.sh into three focused scripts:
- check-title-length.sh: title must be <= 80 chars
- check-no-fixup.sh: no fixup/squash/WIP commits
- check-commit-body.sh: body required for 20+ line changes

All scripts skip merge commits via --no-merges to avoid
false positives on GitHub's auto-generated merge commit
titles.

Author: dannywillems

.github/scripts/pr-hygiene/check-commit-body.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# Check that commits with 20+ lines changed include a non-empty body.
+# Skips merge commits.
+#
+# Usage: check-commit-body.sh <base-sha>
+set -euo pipefail
+
+base="${1:?Usage: check-commit-body.sh <base-sha>}"
+errors=0
+
+for commit in $(git log --no-merges --format=%H "${base}..HEAD"); do
+    short=$(git log -1 --format=%h "$commit")
+    body=$(git log -1 --format=%b "$commit")
+
+    lines_changed=$(git diff-tree --no-commit-id --numstat -r "$commit" \
+        | awk '{ s += $1 + $2 } END { print s+0 }')
+    body_trimmed=$(echo "$body" | sed '/^$/d' | head -1)
+
+    if [ "$lines_changed" -ge 20 ] && [ -z "$body_trimmed" ]; then
+        echo "::error::Commit $short: $lines_changed lines changed but no commit body."
+        echo "  Commits with 20+ lines changed should include a description."
+        errors=$((errors + 1))
+    fi
+done
+
+if [ "$errors" -gt 0 ]; then
+    echo "Found $errors commit(s) missing a body."
+    exit 1
+fi
+
+echo "All large commits have a body."

.github/scripts/pr-hygiene/check-commit-messages.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Check that no fixup/squash/WIP commits remain in the PR.
+# Skips merge commits.
+#
+# Usage: check-no-fixup.sh <base-sha>
+set -euo pipefail
+
+base="${1:?Usage: check-no-fixup.sh <base-sha>}"
+errors=0
+
+for commit in $(git log --no-merges --format=%H "${base}..HEAD"); do
+    subject=$(git log -1 --format=%s "$commit")
+    short=$(git log -1 --format=%h "$commit")
+
+    case "$subject" in
+        fixup!*|squash!*|WIP:*|WIP\ *|wip:*|wip\ *)
+            echo "::error::Commit $short: fixup/squash/WIP commits must be cleaned up before merge."
+            echo "  Title: $subject"
+            errors=$((errors + 1))
+            ;;
+    esac
+done
+
+if [ "$errors" -gt 0 ]; then
+    echo "Found $errors fixup/WIP commit(s)."
+    exit 1
+fi
+
+echo "No fixup/squash/WIP commits found."

.github/scripts/pr-hygiene/check-no-fixup.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# Check that commit titles do not exceed 80 characters.
+# Skips merge commits.
+#
+# Usage: check-title-length.sh <base-sha>
+set -euo pipefail
+
+base="${1:?Usage: check-title-length.sh <base-sha>}"
+errors=0
+
+for commit in $(git log --no-merges --format=%H "${base}..HEAD"); do
+    subject=$(git log -1 --format=%s "$commit")
+    short=$(git log -1 --format=%h "$commit")
+
+    title_len=${#subject}
+    if [ "$title_len" -gt 80 ]; then
+        echo "::error::Commit $short: title is $title_len chars (max 80)."
+        echo "  Title: $subject"
+        errors=$((errors + 1))
+    fi
+done
+
+if [ "$errors" -gt 0 ]; then
+    echo "Found $errors title length error(s)."
+    exit 1
+fi
+
+echo "All commit titles are within 80 characters."

.github/scripts/pr-hygiene/check-title-length.sh

@@ -27,7 +27,15 @@ jobs:
       - uses: actions/checkout@v6
         with:
           fetch-depth: 0
-      - name: Verify commit message quality
+      - name: Check title length
         run: >
-          .github/scripts/pr-hygiene/check-commit-messages.sh
+          .github/scripts/pr-hygiene/check-title-length.sh
+          "${{ github.event.pull_request.base.sha }}"
+      - name: Check no fixup/WIP commits
+        run: >
+          .github/scripts/pr-hygiene/check-no-fixup.sh
+          "${{ github.event.pull_request.base.sha }}"
+      - name: Check commit body on large changes
+        run: >
+          .github/scripts/pr-hygiene/check-commit-body.sh
           "${{ github.event.pull_request.base.sha }}"