hadley/ggplot2 — pull request #505 by jiho (2012-04-19 11:38:54+00:00)
Title: Allow alpha to affect colour

For all filled shapes (polygons, reactangles, etc.) alpha affected fill only.
One could set the stroke to be a transparent colour using

colour=scales::alpha("blue", 0.5)

outside of aes() for example. But there was no way to map the colour of the
stroke to a semi transparent colour. This commit fixes it.