Merge branch 'ar/decorate-color'

Merge branch 'ar/decorate-color'

* ar/decorate-color:
  Add test for correct coloring of git log --decoration
  Allow customizable commit decorations colors
  log --decorate: Colorize commit decorations
  log-tree.c: Use struct name_decoration's type for classifying decoration
  commit.h: add 'type' to struct name_decoration