BASH script used as GIT tree-filter to fix the coding style of all commits on the branch

cke-branch-rewriter.sh

#!/bin/sh
set -e
echo ""

# Copied from the git source code as the filter-branch map function is not exposed to scripts.
map()
{
	# if it was not rewritten, take the original
	if test -r "../map/$1"
	then
		cat "../map/$1"
	else
		echo "$1"
	fi
}

DIR="$(dirname $0)"

# Get the old master commit hash.
OLD_MASTER=$( git rev-parse --quiet --verify master-before-codefix )

# Get the manual fixing commit on new master.
POST_FIX=$( git log --format="%H" --grep 'Post-fix on the code style rewritting.' master )

# Check if the current branch has been properly rebased.
if [ "$(git rev-parse $OLD_MASTER )" != "$(git merge-base $OLD_MASTER HEAD)" ]
then
	echo ""
	echo "ERROR: Please rebase branch onto master-before-codefix first."
	echo ""
	exit 1;
fi

# For some reason, I was not able to use grep here to filter .js files straight.
FILES=$( git ls-files )

if git rev-parse --quiet --verify $GIT_COMMIT^ >/dev/null
then
	# If there is a previous commit, take the reference for the rewritten on.
	PREVIOUS_ORI=$( git rev-list $GIT_COMMIT -n 1 --skip 1 )
	PREVIOUS=$( map $PREVIOUS_ORI )

	if [ $PREVIOUS == $OLD_MASTER ]
	then
		# Use master as the base if this is the first commit in the branch.
		PREVIOUS="master"
	fi

	# Make a full copy of the parent commit.
	git checkout $PREVIOUS -- .

	# Get the list of changed files.
	TOUCHED=$( git show --name-only --pretty="format:" $GIT_COMMIT | grep "[^\s]" )
else
	# For the initial commit, all files are touched.
	TOUCHED=$FILES
fi

for t in $TOUCHED
do

	# Checkout touched files.
	git checkout -f $GIT_COMMIT $t

	# Fix JS files.
	if [ -f "$t" ] && [ ${t##*.} == "js" ]
	then
		echo "Fixing JS file $t, from commit:`git log --pretty="%s" -1 $GIT_COMMIT`"
		# 1. Run beautifier.
		js-beautify -o $t $t

		# 2. Apply manual fixes broken by beautifier.
		CHANGED=$(git diff --name-only "$POST_FIX^" "$POST_FIX" $t)
		if [ -n "$CHANGED" ];
		then
			git diff "$POST_FIX^" "$POST_FIX" $t | git apply
		fi
	fi
done

echo ""