- '%Cgreen': switch color to green
- '%Cblue': switch color to blue
- '%Creset': reset color
-- '%C(...)': color specification, as described in color.branch.* config option;
+- '%C(...)': color specification, as described under Values in the
+ "CONFIGURATION FILE" section of linkgit:git-config[1];
adding `auto,` at the beginning will emit color only when colors are
enabled for log output (by `color.diff`, `color.ui`, or `--color`, and
respecting the `auto` settings of the former if we are going to a