God Dog was written by Robin Williamson and recorded with the Incredible String Band in 1967 but not released at that time. He gave it to Shirley Collins though, who sang it in 1969 on her and her sister Dolly's album Anthems in Eden. This recording was also included on her anthologies A Favourite Garland (1974) and Within Sound (2002). She quoted Robin Williamson from an interview for Swing 51 magazine in her 2018 book All in the Downs (p. 128):
I thought it would be every suitable song for Shirley to sing because I'd always liked her voice. To me it's a very natural voice and because God Dog is such an innocent song—it's a child song really, I didn't know anyone else who would be able to sing it. In the end, I guess I more or less wrote it for her.
The original Incredible String Band track was finally published in 1998 on their CD The Chelsea Sessions 1967. It was also included in 2005 on Castle Music's 4 CD folk anthology Anthems in Eden.
Jack Sharp learned God Dog from Shirley and Dolly Collins' 1969 album. He recorded it in 2020 for his album Good Times Older.
Sorry, I can't show the lyrics here as I don't have the copyright owners' permission to publish them. But please feel free and ask me to send you the song's lyrics.