Regexp - joining multiple lines not starting with dash

Question

I have lines that look like this:

- test 1
  test test test
  test test test
  test test test
- test2
- test3
  test test t
  test test test
- test 4
  test test test
- test5

I am looking for a regexp to convert them into this:

- test 1
  test test test test test test test test test
- test2
- test3
  test test t test test test
- test 4
  test test test
- test5

That is to remove all new line after each line that does not begin with \s*?\- and that does not precede a line that begins with \s*?\-

Answer 1

How about something like

^(\h*[^-\s].*)\R(?!-)

and replace with $1

• ^ matches line start
• (\h*[^-\s].*) first group captures: Any amount of h-space followed by a character, that is not - or \s whitespace, followed by any amount of any characters
• \R(?!-) newline sequence that's not followed by a hyphen

See this demo at regex101

For joining parts by just one space see this version and replace with $1 (a bit less efficient).