When does single_line_zle get set?

[Dan Nelson <dnelson@xxxxxxxx>]

I just compiled zsh-2.6beta9 (was using 2.6beta-3), and now, on initial
login shells, single_line_zle mode gets set on me.  I login to an ISP via
modem, and my terminal defaults to 'unknown'.  It seems that zsh notices
this and sets single_line_zle (-M) on me.

According to the zshzle man page:

: There are two display modes.  The first, multiline mode, is the default. 
: It only works if the TERM parameter is set to a valid terminal type that
: can move the cursor up.  The second, single line mode, is used if TERM is
: invalid or incapable of moving the cursor up, or if the SINGLE_LINE_ZLE
: option is set.  This mode is similar to ksh, and uses no termcap sequences. 

The shell, however, sets the SINGLE_LINE_ZLE option _if_ "TERM is invalid or
capable of moving the cursor up".  Not quite what the man page states.

I don't quite understand why the change was made.  Anyone logging in on a
machine that sets the terminal type to 'dumb/network/unknown' must now
manually unset single_line_zle mode.

	-Dan Nelson
	dnelson@xxxxxxxx