Try This

\version "2.18.2"
\header {
      encodingdate = "2018-06-19"
      title = "The Kesh Jig"
      subtitle = " "}
       \relative d' {\key g \major \time 6/8
       \repeat volta 2 {
       \partial8
            d8 | g4.^"~"^"G" g8 a b | a ^"D" b a a b d | e ^"C" d d g^"G/B" d d | e^"Am" d b d^"D7/F#" b a \break
            g4.^"~"^"G" g8 a b | a^"D" b a a b d | e^"Am" d d g^"G" d b | a^"D/F#" g fis g4^"G" } \break
       \repeat volta 2 {
       \partial8
            a8 | b4.^"~"^"Em" d8^"G" b d | e^"C" g e d^"G" b a | b4.^"~"^"Em" d8^"G" b g | a^"D7" b a a g a | \break
            b^"Em" a b d^"G" b d | e^"C" g e d^"G" b d | g^"C" fis g a^"D7" g a | b^"G" g fis g4 }                 
       }

It is getting a bit longer, partly because I fiddled with the chords. There's still one warning about the 'partial' part way through. This sets the anacrusis at the start of the second part so may be there is a better way of doing this.