Undocumented ex/vi options

[D A Mercer]

> Does anyone know what the "sourceany", "tagstack" and "timeout"
> options of ex/vi do? 

     timeout - ex/vi sets a one second timer upon input of special
	 characters (copied from curses); if all the characters are
	 not received within the time slice,  an error is generated and
	 subsequent characters in a multi character sequence (such as the
	 cursor keys for a vt100) are clocked in as normal command characters.
	 For instance, cursor right (<ESC>[C) can delete characters and leave
	 you in input mode.  Since in UNIX,  a 1 second time slice is the
	 interval between the last 1 second interval expiration and the next,
	 and is thus usually less than 1 second,  cursor keys are frequently
	 scrambled,  even at 19.2.  Setting notimeout prevents this,  bu has
	 its own side effects.  For instance,  if you have the erase to
	 end of file key defined for an ADDS Viewpoint 90 (<ESC>G),  trying
	 to exit input mode and branching to the end of the file can result
	 in erasing to the end of file.  Two escapes have to be entered to
	 be sure of exitting input mode.  All of this derives from ex being
	 single character oriented and only supporting multi character key
	 input as macros.