Count the number of commits per quarter having a message that ends up with parentheses and certain specific characters

commits_per_quarter.sh

#!/usr/bin/env bash

for (( year=$1; year<=$2; year++ ))
do
  echo -n "Q1 $year:"
  git log --oneline --after="$year-01-01" --until="$year-04-01" | grep "([[:alnum:] ,\.]\+)$"  | wc -l
  echo -n "Q2 $year:"
  git log --oneline --after="$year-04-01" --until="$year-07-01" | grep "([[:alnum:] ,\.]\+)$"  | wc -l
  echo -n "Q3 $year:"
  git log --oneline --after="$year-07-01" --until="$year-10-01" | grep "([[:alnum:] ,\.]\+)$"  | wc -l
  echo -n "Q4 $year:"
  git log --oneline --after="$year-10-01" --until="$((year+1))-01-01" | grep "([[:alnum:] ,\.]\+)$"  | wc -l
done