pre-commit-whitespace

#!/usr/bin/env bash

for file in `git diff --name-only --cached --diff-filter=d | grep '\.py$'`; do
    echo "whitespace: processing $file"
    if `git diff --quiet "$file"`; then
        # no dirty version in working tree,
        # edit the file directly and git-add
        # 1. remove trailing whitespace
        sed -i '' -E 's/[[:space:]]*$//' "$file"
        # 2. replace tabs with 4 spaces
        sed -i '' $'s/\t/    /g' "$file"
        # 3. check file ends with two newlines
        # TODO
        git add --verbose "$file"
    else
        # need to leave working tree untouched, so 
        # save staged contents of file to temp file
        # and process that
        git show ":$file" > "$file.ws.tmp"
        sed -i '' -E 's/[[:space:]]*$//' "$file.ws.tmp"
        sed -i '' $'s/\t/    /g' "$file.ws.tmp"
        # manually create the blob from modified temp
        # file and update the original file in the index
        hash=`git hash-object -w "$file.ws.tmp"`
        git update-index --add --verbose --cacheinfo 100644 "$hash" "$file"
        # cleanup after yourself!
        rm "$file.ws.tmp"
    fi
done

# If no files left in index after formatting - fail
ret=0
if `git diff --staged --quiet`; then
    1>&2 echo "whitespace: No files to commit after trimming whitespace."
    exit 1
fi