daz:~$ cat test
gsdfg sdg sdg sdg dfg dfg df-
dgdf gsd gdf gsd gsd gsdfgsd-
dsfg-sdg sdf-g sdf-g sdfg-sdgsfd
sdfgdfg
dfgdf
gdfhdfhf h dfh fgh f
h fdh df-h fgfd-
-fgdg
start - - - - - - - - - - - - - - - - - end

daz:~$ cat test | tr "\n" " " | sed 's/- //g'
gsdfg sdg sdg sdg dfg dfg dfdgdf gsd gdf gsd gsd gsdfgsddsfg-sdg sdf-g sdf-g sdfg-sdgsfd sdfgdfg dfgdf gdfhdfhf h dfh fgh f h fdh df-h fgfd-fgdg start end 

daz:~$ sed "s/-$//" test|xargs                   
gsdfg sdg sdg sdg dfg dfg df dgdf gsd gdf gsd gsd gsdfgsd dsfg-sdg sdf-g sdf-g sdfg-sdgsfd sdfgdfg dfgdf gdfhdfhf h dfh fgh f h fdh df-h fgfd -fgdg start - - - - - - - - - - - - - - - - - end