Git post-update hook: After $TARGET_REF is pushed, write the contents of $FILE to $DEST.

git-post-update-copy-file.sh

#!/bin/sh
#
# After $TARGET_REF is pushed, write the 
# contents of $FILE to $DEST.
#
# To enable this hook in a bare git repo
#   1. place it in the hooks/ directory
#   2. rename it to "post-update"
#   3. chmod +x post-update

TARGET_REF=refs/heads/master
FILE=README.md
DEST=/tmp/README.md

for ref in "$@"
do
	if [[ $ref == $TARGET_REF ]]; then
		echo "'$TARGET_REF' updated, copying '$FILE' to '$DEST'"
		git show $TARGET_REF:$FILE > $DEST
		echo "Done"
	fi
done