[git-tools] Improvements for the pre-commit hook

One major issue with the pre-hook so far was partially staged files,
because it used filenames for php lint. These changes will make the hook read the file contents from the index instead.

Great thanks to David Soria Parra.

git-tools/hooks/pre-commit

@@ -25,12 +25,35 @@ fi
 
 error=0
 
-# get a list of staged .php files, omitting file removals
-IFS=" "
-for file in $(git diff --cached --name-status $against | grep -v -E '^D' | cut -f2 | grep -E '\.php$')
+IFS=$'\n'
+# get a list of staged files
+for line in $(git diff-index --cached --full-index $against)
 do
-	# hide output, but show errors
-	if ! $PHP_BIN -l "$file" >/dev/null
+	# split needed values
+	sha=$(echo $line | cut -d' ' -f4)
+	temp=$(echo $line | cut -d' ' -f5)
+	status=$(echo $temp | cut -d'	' -f1)
+	filename=$(echo $temp | cut -d'	' -f2)
+
+	# file extension
+	ext=$(echo $filename | sed 's/^.*\.//')
+
+	# only check files with php extension
+	if [ $ext != "php" ]
+	then
+		continue
+	fi
+
+	# do not check deleted files
+	if [ $status = "D" ]
+	then
+		continue
+	fi
+
+	# check the staged file content for syntax errors
+	# using php -l (lint)
+	git cat-file -p $sha | $PHP_BIN -l >/dev/null
+	if [ $? -ne 0 ]
 	then
 		error=1
 	fi