List git changes by filetype pattern for an author

commits.sh

#!/bin/sh

author=$1; shift;
patterns=( "$@" );

function get_commits() {
    git log --author=$1 --pretty=tformat: --numstat \
      | grep $2 \
      | awk '{ add += $1; subs += $2; loc += $1 - $2 }
        END {
            printf "+%s, -%s, %s total (%s:1 +/- ratio)\n",
            add, subs, loc, sprintf("%.2f", add / subs)
        }'
}

for i in "${patterns[@]}"
do
    echo "\nChanges for pattern \"$i\"";
    get_commits $author $i;
done

Lists how many changes the author david has made where the file name ends with .scala

❯ ./commits.sh david ".scala$"

Changes for pattern ".scala$"
+2348, -1330, 1018 total (1.77:1 +/- ratio)

Also allows passing multiple patterns, where first argument is the author name and subsequent arguments are patterns to match against. Useful for comparing across languages, for example:

❯ ./commits.sh david ".scss$" ".js$" ".scala$"

Changes for pattern ".scss$"
+13743, -13703, 40 total (1.00:1 +/- ratio)

Changes for pattern ".js$"
+2969, -2567, 402 total (1.16:1 +/- ratio)

Changes for pattern ".scala$"
+2348, -1330, 1018 total (1.77:1 +/- ratio)