remove endasheds at linebreaks

remove endasheds at linebreaks

I want to typeset a paragraph of endash-separated expressions, like this
\documentclass{article}
\setlength{\parindent}{0pt}
\begin{document}
\centering
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test -- test -- test -- test -- test -- test --
test -- test -- test -- test
\end{document}
However, I don't want the endashes to be printed as first or last items in
a line - in a way, I want them to behave like spacing commands (blank,
\hfil, \hfill, \hfilll).
So instead of this
test - test - test -
test - test - test
or this
test - test - test
- test - test - test
I want this
test - test - test
test - test - test
Please note that I want this to happen automatically, without having to
fix each line manaully
How can this be achieved?