(This is mainly a remainder post for myself)
For certain reasons I sometimes have to edit text pasted from an emacs buffer that I was editing with the longlines-mode enabled. Hence as this mode does, the paragraphs are hard wrapped beyond a certain amount of characters (when they extend over ‘fill-column’ lenght).
Although “the soft newlines used for line wrapping will not show up when the text is yanked or saved to disk”, they will remain if, say, I had carelessly pasted it directly into a gmail form to save for later reuse there.
My way to remove those artificially-inserted line breaks, is running this oneliner on the text region.
sed -ne '1h;1!H;${;g;s#\n\([^\n]\)# \1#g;p}' | sed -e 's#^[ \t]*\(.*\)$#\1#g'
(The first sed command tells to put a space and remove the line break. using the multiline search and replace method
The second just gets rid of the leading white space at the beginning of line)