evolve: extract cleanup logic in the evolve function
We are going to need to reuse the cleanup logic when introducing --rev, so
we extract it in a method to avoid code duplication.
all: tutorials/tutorial.rst static/logo-evolve.ico
sphinx-build . ../html/
tutorials/tutorial.rst: tutorials/tutorial.t
python test2rst.py tutorials/
static/logo-evolve.ico: static/logo-evolve.svg
convert -resize 36x36 static/logo-evolve.svg static/logo-evolve.ico