List Authors by Commit Count

# Commits per author, all-time
git shortlog -sn --no-merges

# Same, but restrict to a date range
git shortlog -sn --no-merges --since="1 year ago"

# Lines added + removed per author
git log --pretty=tformat: --numstat --no-merges \
    | awk '/^[0-9]+\t[0-9]+/ {add+=$1; del+=$2} END {printf "+%d / -%d\n", add, del}'

# Per-author lines added/removed (slower)
git log --pretty='format:%an' --numstat --no-merges \
    | awk '/^[^0-9]/ {a=$0; next} /^[0-9]+\t[0-9]+/ {add[a]+=$1; del[a]+=$2}
           END {for (n in add) printf "%-25s +%6d  -%6d\n", n, add[n], del[n]}'