home/git: add author-lines script

home/programs/git/scripts/git-author-lines.sh

@@ -0,0 +1,19 @@
+set -euo pipefail
+
+if [ -n "${1:-}" ]; then
+  REF="${1}"
+else
+  REF="HEAD"
+fi
+
+# TODO: optionally keep track of which files the authors were present in,
+#       and print a list of up to N files where the authors contributed the most.
+
+git ls-tree -r "${REF}" \
+| while read -r _filemode _objtype _githash filepath; do
+  git blame --line-porcelain "${filepath}"
+done \
+| grep --binary-files=without-match '^author ' \
+| sed -e 's/author //' \
+| awk '{ a[$0]+=1 } END{ for (i in a) { print a[i],i } }' \
+| sort --numeric-sort --key 1 --reverse