contributions.awk

BEGIN {
    FS = OFS = "\t"
}
$0 == "" { next }
NF == 2 {
    current_author = $1
    commits[current_author]++
    next
}
NF == 3 {
    insertions[current_author] += ($1 + 0)
    deletions[current_author] += ($2 + 0)
    files[current_author][$3] = 1
    next
}
{
    print "Unexpected line (NR=" NR "): " $0 > "/dev/stderr"
    current_author = "Unknown"
}
END {
    print "Author", "Commits", "UniqueFiles", "Insertions", "Deletions"
    for (author in commits)
        print author, commits[author], length(files[author]), insertions[author] + 0, deletions[author] + 0
}

pipe.bash

git log --pretty=format:$'"%aN"\t%H' --numstat --no-merges | awk -f contributions.awk > contributors.tsv