slur attachment

[David Bobroff]

In this short snippet I want the start of the slur to be attached to the
stem of the starting note and the head of the ending note.  I took the
\override command directly from the current docs but it is having no
effect.  In the output it is attached to the heads at both ends.

-David


    \context Voice \relative c' {
        \clef F
         \override Slur #'attachment = #'(stem . head)
        r2 g,2^( ~ 
        g2. a8 b
        c4 d8 e-) r2
    }