My pre-commit Git Hook

pre-commit

# Contents of ~/gitconfig/hooks/pre-commit
# Replace `last_modified_at` timestamp with current time in the specified TZ for .md edits only
# Note that this file should exist on your workstation as `~/gitconfig/hooks/pre-commit` and the file must be executable!

git diff --cached --name-status | egrep -i "^(A|M).*\.(md)$" | while read a b; do
  cat $b | sed "/---.*/,/---.*/s/^last_modified_at:.*$/last_modified_at: $(TZ=CST6CDT date "+%Y-%m-%dT%H:%M:%S")/" > tmp
  mv tmp $b
  git add $b
done