Git pre-commit hook that automatically removes trailing whitespace

pre-commit

#!/bin/bash
#

# A git hook script to find and fix trailing whitespace
# in your commits. Bypass it with the --no-verify option
# to git-commit
#
# usage: make a soft link to this file, e.g., ln -s ~/config/pre-commit.git.sh ~/some_project/.git/hooks/pre-commit

# detect platform
platform="win"
uname_result=`uname`
if [ "$uname_result" = "Linux" ]; then
  platform="linux"
elif [ "$uname_result" = "Darwin" ]; then
  platform="mac"
fi

# change IFS to ignore filename's space in |for|
IFS="
"
# autoremove trailing whitespace
for line in `git diff --check --cached | sed '/^[+-]/d'` ; do
  # get file name
  if [ "$platform" = "mac" ]; then
    file="`echo $line | sed -E 's/:[0-9]+: .*//'`"
  else
    file="`echo $line | sed -r 's/:[0-9]+: .*//'`"
  fi
  # display tips
  echo -e "removing trailing whitespace in \033[31m$file\033[0m!"
  # since $file in working directory isn't always equal to $file in index, so we backup it
  mv -f "$file" "${file}.save"
  # discard changes in working directory
  git checkout -- "$file"
  # remove trailing whitespace
  if [ "$platform" = "win" ]; then
    # in windows, `sed -i` adds ready-only attribute to $file(I don't kown why), so we use temp file instead
    sed 's/[[:space:]]*$//' "$file" > "${file}.bak"
    mv -f "${file}.bak" "$file"
  elif [ "$platform" == "mac" ]; then
    sed -i "" 's/[[:space:]]*$//' "$file"
  else
    sed -i 's/[[:space:]]*$//' "$file"
  fi
  git add "$file"
  # restore the $file
  sed 's/[[:space:]]*$//' "${file}.save" > "$file"
  rm "${file}.save"
done

if [ "x`git status -s | grep '^[A|D|M]'`" = "x" ]; then
  # empty commit
  echo
  echo -e "\033[31mNO CHANGES ADDED, ABORT COMMIT!\033[0m"
  exit 1
fi

# Now we can commit
exit

To enable, just add this to your repository's .git/hooks/pre-commit and chmod +x on it as well.