Avoid joining 1 line in the "nested map" case
Avoid joining 1 line in the "nested map" case

This avoids the following sequence of joins:

list:
  - 1
list:
  - { 1 }
list:
  - { { 1 } }

The "1" is not really a map, but because the "lines" contains it, it
ends up being turned into one, sort of.

AndrewRadev/splitjoin.vim