git clean and smudge linter

#!/bin/bash

# This script is a git clean filter (https://git-scm.com/book/en/v2/Customizing-Git-Git-Attributes#filters_b)
# This will run when files are staged (specifically for all *.py files as defined in the .gitattributes file)
# The point of this script will be to lint our python files with Python Black, and iSort upon committing them

# This script takes in stdin data and expects stdout data. So in order to run black and iSort on the input
# data, we need to save the data into a file somewhere, process that, and then output the results

# Because this expects stdout, we can't let any of our commands output any data, so we just pipe them to
# /dev/null. Unfortunatley this means that we won't get to see any errors.
# Because of this, this script will fallback to output the original data if any error occurs.

# Make a temporary file to store the stdin code
tmpfile=$(mktemp)
tmplint=$(mktemp)

# The "file" is either stdin, or an argument (not sure we need this)
file=${1--}

# Read in the stdin data into our temp files
while IFS= read -r line ; do
    echo "$line" >> "$tmpfile"
    echo "$line" >> "$tmplint"
done < <(cat -- "$file")

# Keep a status variable. If either command returns a non zero
# then we just return the original input
rc=0

# Run black and iSort on our modified temp file
isort $tmplint > /dev/null 2>&1
if [ $? -ne 0 ] ; then
    rc=1
fi

black $tmplint > /dev/null 2>&1
if [ $? -ne 0 ] ; then
    rc=1
fi

# Check the return codes
if [ $rc -ne 0 ] ; then
    # If we had a bad exit, then just cat the original input
    cat $tmpfile
else
    # else we cat the linted contents
    cat $tmplint
fi

# Remove the temp files
rm $tmpfile > /dev/null 2>&1
rm $tmplint > /dev/null 2>&1

exit 0