TWiki::UI::Edit UI::run method.
Most parameters are in the CGI query:
 cmd  | 
			Undocumented save command, passed on to save script | 
 onlywikiname  | 
			if defined, requires a wiki name for the topic name if this is a new topic | 
 onlynewtopic  | 
			if defined, and the topic exists, then moans | 
 formtemplate  | 
			name of the form for the topic; will replace existing form | 
 templatetopic  | 
			name of the topic to copy if creating a new topic | 
 skin  | 
			skin(s) to use | 
 topicparent  | 
			what to put in the topic prent meta data | 
 text  | 
			text that will replace the old topic text if a formtemplate is defined (what the heck is this for?) | 
 contenttype  | 
			optional parameter that defines the application type to write into the CGI header. Defaults to text/html. | 
 action  | 
			Optional. If supplied, use the edit${action} template instead of the standard edit template. An empty value means edit both form and text, "form" means edit form only, "text" means edit text only |