Some people feel the default set of colors used by "git log --graph"
rather limiting. A mechanism to customize the set of colors has
been introduced.
* nd/log-graph-configurable-colors:
document behavior of empty color name
color_parse_mem: allow empty color spec
log --graph: customize the graph lines with config log.graphColors
color.c: trim leading spaces in color_parse_mem()
color.c: fix color_parse_mem() with value_len == 0