+By default, filters are separate processes that are executed each time they
+are needed. Alternative technologies may be used by prefixing the filter
+specification with the relevant string; available values are:
+
+'exec:'::
+ The default "one process per filter" mode.
+
+'lua:'::
+ Executes the script using a built-in Lua interpreter. The script is
+ loaded once per execution of cgit, and may be called multiple times
+ during cgit's lifetime, making it a good choice for repeated filters
+ such as the 'email filter'. It responds to three functions:
+
+ 'filter_open(argument1, argument2, argument3, ...)'::
+ This is called upon activation of the filter for a particular
+ set of data.
+ 'filter_write(buffer)'::
+ This is called whenever cgit writes data to the webpage.
+ 'filter_close()'::
+ This is called when the current filtering operation is
+ completed. It must return an integer value. Usually 0
+ indicates success.
+
+ Additionally, cgit exposes to the Lua the following built-in functions:
+
+ 'html(str)'::
+ Writes 'str' to the webpage.
+ 'html_txt(str)'::
+ HTML escapes and writes 'str' to the webpage.
+ 'html_attr(str)'::
+ HTML escapes for an attribute and writes "str' to the webpage.
+ 'html_url_path(str)'::
+ URL escapes for a path and writes 'str' to the webpage.
+ 'html_url_arg(str)'::
+ URL escapes for an argument and writes 'str' to the webpage.
+ 'html_include(file)'::
+ Includes 'file' in webpage.
+
+
+Parameters are provided to filters as follows.
+