Some trick to allow empty dir

plugins/htmlpurifier/standalone/HTMLPurifier/DefinitionCache/Serializer/CSS/.gitignore

@@ -0,0 +1,4 @@
+# Ignore everything in this directory
+*
+# Except this file
+!.gitignore

plugins/htmlpurifier/standalone/HTMLPurifier/DefinitionCache/Serializer/HTML/.gitignore

@@ -0,0 +1,4 @@
+# Ignore everything in this directory
+*
+# Except this file
+!.gitignore

plugins/htmlpurifier/standalone/HTMLPurifier/DefinitionCache/Serializer/Test/.gitignore

@@ -0,0 +1,4 @@
+# Ignore everything in this directory
+*
+# Except this file
+!.gitignore

plugins/htmlpurifier/standalone/HTMLPurifier/DefinitionCache/Serializer/URI/.gitignore

@@ -0,0 +1,4 @@
+# Ignore everything in this directory
+*
+# Except this file
+!.gitignore