CI: Require a blank line between commit titles and bodies

.github/workflows/lintcommits.yml

@@ -20,6 +20,10 @@ jobs:
                 pattern: /^[^\r]*$/,
                 error: "Commit message contains CRLF line breaks (only unix-style LF linebreaks are allowed)",
               },
+              {
+                pattern: /^.+(\r?\n(\r?\n.*)*)?$/,
+                error: "Empty line between commit title and body is missing",
+              },
               {
                 pattern: /^.{0,72}(?:\r?\n(?:(.{0,72})|(.*?([a-z]+:\/\/)?(([a-zA-Z0-9_]|-)+\.)+[a-z]{2,}(:\d+)?([a-zA-Z_0-9@:%\+.~\?&/=]|-)+).*?))*$/,
                 error: "Commit message lines are too long (maximum allowed is 72 characters, except for URLs)",

Meta/lint-commit.sh

@@ -30,6 +30,10 @@ while read -r line; do
   ((line_number += 1))
   line_length=${#line}
 
+  if [[ $line_number -eq 2 ]] && [[ $line_length -ne 0 ]]; then
+    error "Empty line between commit title and body is missing"
+  fi
+
   category_pattern="^\S.*?\S: .+"
   if [[ $line_number -eq 1 ]] && (echo "$line" | grep -E -v -q "$category_pattern"); then
     error "Missing category in commit title (if this is a fix up of a previous commit, it should be squashed)"