Merge branch 'mm/color-auto-default'

Flip the default for color.ui to 'auto', which is what many
tutorials recommend new users to do.

* mm/color-auto-default:
  make color.ui default to 'auto'
  config: refactor management of color.ui's default value

diff --cc Documentation/config.txt
Simple merge

diff --cc builtin/config.c
Simple merge