I have a curved path that I want to put an open diamond arrow tip on.  Here is a MWE with my best attempt:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows,decorations.markings}
\begin{document}
 \begin{tikzpicture}[decoration={
   markings,
   mark=at position .5 with {\arrow[&gt;=open diamond] {&gt;} } }
  ]
  \node (0)                     {};
  \node (1) [right       of=0]  {};
  \node (2) [below right of=1]  {};
  \path (0) edge[out=0, in=135, postaction={decorate}] (2);
 \end{tikzpicture}
\end{document}




As you can see, the bottom-right point of the diamond is perfectly on the path, but the top-left point is clearly above the path.  It appears that the diamond lies on the tangent line of the path at the bottom-right point of the diamond.

Question:

How can I place this open diamond arrow tip so that both points of the diamond are on the path?

Bonus Question:

What is the best solution to make the area inside the diamond completely white? I don't want to see the path in the inside of the diamond.  I currently have a solution that I feel is a hack, which is to place a white (closed) diamond arrow tip in the same spot first:

mark=at position .5 with {\arrow[&gt;=diamond, white] {&gt;} },



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