ci(commitlint): fix local running of commit linter on macOS (#427)

Replaces GNU-specific `grep` command-line option in the commitlint check
so that the linter would work locally on both macOS and Linux operating
systems.

Author: tiborsimko

run-tests.sh

@@ -20,17 +20,17 @@ check_commitlint () {
         commit_title=$(echo "$line" | cut -d ' ' -f 2-)
         commit_number_of_parents=$(git rev-list --parents "$commit_hash" -n1 | awk '{print NF-1}')
         # (i) skip checking release commits generated by Release Please
-        if [ "$commit_number_of_parents" -le 1 ] && echo "$commit_title" | grep -qP "^chore\(.*\): release"; then
+        if [ "$commit_number_of_parents" -le 1 ] && echo "$commit_title" | grep -qE "^chore\(.*\): release"; then
             continue
         fi
         # (ii) check presence of PR number
-        if ! echo "$commit_title" | grep -qP "\(\#$pr\)$"; then
+        if ! echo "$commit_title" | grep -qE "\(#$pr\)$"; then
             echo "✖   Headline does not end by '(#$pr)' PR number: $commit_title"
             found=1
         fi
         # (iii) check absence of merge commits in feature branches
         if [ "$commit_number_of_parents" -gt 1 ]; then
-            if echo "$commit_title" | grep -qP "^chore\(.*\): merge "; then
+            if echo "$commit_title" | grep -qE "^chore\(.*\): merge "; then
                 break  # skip checking maint-to-master merge commits
             else
                 echo "✖   Merge commits are not allowed in feature branches: $commit_title"