Only show current working directory in the path

[BrambleXu]

Even if I set the POWERLINE_PATH="short", it is still too long for some path, like smap10@Xu ~/Project/Relation-Extraction/relation-classication-cnn-pytorch

Is ther any way only show the current working directory, like this

smap10@Xu .../Relation-Extraction/relation-classication-cnn-pytorch

or

smap10@Xu ~/.../relation-classication-cnn-pytorch