Get a contributions summary for an author prior to a date

author_summary.sh

AUTHOR=$1
FIRST_DAY=$2
echo "First contribution of $AUTHOR was done on: `git log --reverse --author="$AUTHOR" --until "$FIRST_DAY" -n 1 --pretty=%aI`"
CONTRIBUTIONS_SUMMARY=`git log --author="$AUTHOR" --pretty=tformat: --numstat --until "$FIRST_DAY" \
 | awk '{ add += $1; subs += $2; loc += $1 - $2 } END \
  { printf "added lines(+): %s; removed lines(-): %s, total lines: %s\n", add, subs, loc }'`

echo "Contributions until $FIRST_DAY: $CONTRIBUTIONS_SUMMARY"