[ci] Support XODO comments in commit messages (#2998)

(s/X/T/, of course)

This allows us to leave general XODOs in commit messages that don't
naturally belong in any particular file, and PR merging will be blocked
until they are removed.

gherrit-pr-id: Gc456c89ea3f26105fca5cadcd11ddc5107ed6afe

Author: joshlf

ci/check_todo.sh

@@ -24,7 +24,14 @@ rg --version >/dev/null
 # -n: Print line number
 # -w: Match whole words
 # Match TODO, TODO-check-disable, and TODO-check-enable
-output=$(rg -H -n -w "$KEYWORD|$KEYWORD-check-disable|$KEYWORD-check-enable" "$@" || true)
+PATTERN="$KEYWORD|$KEYWORD-check-disable|$KEYWORD-check-enable"
+output=$(rg -H -n -w "$PATTERN" "$@" || true)
+
+commit_output=$(git log -1 --pretty=%B 2>/dev/null | rg -n -w "$PATTERN" || true)
+if [ -n "$commit_output" ]; then
+  commit_output=$(echo "$commit_output" | sed "s/^/COMMIT_MESSAGE:/")
+  output="$commit_output${output:+$'\n'$output}"
+fi
 
 if [ -z "$output" ]; then
   exit 0