#!/usr/bin/env bash
#
# A git commit hook that will automatically append a DCO signoff to the bottom
# of any commit message that doesn't have one. This append happens after the git
# default message is generated, but before the user is dropped into the commit
# message editor.
#
# To enable this hook, run `bootstrap`, or run the following from the root of
# the repo. (Note that `bootstrap` will correctly install this even if this code
# is located in a submodule, while the following won't.)
#
# $ ln -s ../../support/hooks/prepare-commit-msg .git/hooks/prepare-commit-msg

COMMIT_MESSAGE_FILE="$1"
AUTHOR=$(git var GIT_AUTHOR_IDENT)
SIGNOFF=$(echo $AUTHOR | sed -n 's/^\(.*>\).*$/Signed-off-by: \1/p')

# Check for DCO signoff message. If one doesn't exist, append one and then warn
# the user that you did so.
if ! $(grep -qs "^$SIGNOFF" "$COMMIT_MESSAGE_FILE") ; then
  echo -e "\n$SIGNOFF" >> "$COMMIT_MESSAGE_FILE"
  echo -e "Appended the following signoff to the end of the commit message:\n  $SIGNOFF\n"
fi