Github pre-commit hook to prevent commits of large files

pre-commit

#!/bin/sh

# This is a pre-commit hook that ensures attempts to commit files that
# are larger than 100 MB to your _local_ repo fail, with a helpful error
# message.
# 
# This prevents the local repo from getting out of sync with the Github 
# repo. To install
# 1) Change this file to executable: 
#    $ chmod a+x pre-commit
# 2) Move into the .git/hooks directory at the top-level of the repo
#    $ mv pre-commit .git/hooks/
#
# See blog post on https://kiwidamien.github.io/prevent-big-commits

function file_too_large(){
	filename=$0
	# This command is more portable, but harder to reason about
	# filesize=`echo $1 | awk '{ mb =$1 / 1024 / 1024; print mb " MB"}'`
	filesize=$(( $1 / 10**6 ))

	cat <<HEREDOC
	
	File $filename is $filesize MB, which is larger than github's maximum
        file size (100 MB). We will not be able to push this file to Github.

	Commit aborted 
HEREDOC

}


empty_tree=$( git hash-object -t tree /dev/null )
limit=100000000

if git rev-parse --verify HEAD > /dev/null 2>&1
then
	against=HEAD
else
	against=empty_tree
fi

for file in $( git diff-index --cached --name-only $against ); do
	file_size=$( ls -la $file | awk '{ print $5 }')
	if [ "$file_size" -gt  "$limit" ]; then
		file_too_large $filename $file_size
		exit 1;
	fi
done

FYI, another fix picked up by @guysmoilov over here that's prob worth a blog update too.