evolve: use right value for branch name when finding branch heads
subbranch already formatted as "branchname:topicname", again appending it
with ":topicname" doesn't not make sense.
It's a little bit surprising that no tests fails though.
SPHINXBUILD ?= sphinx-build
all: tutorials/tutorial.rst tutorials/topic-tutorial.rst static/logo-evolve.ico
$(SPHINXBUILD) . ../html/
tutorials/tutorial.rst: tutorials/tutorial.t test2rst.py
python test2rst.py tutorials/
tutorials/topic-tutorial.rst: tutorials/topic-tutorial.t test2rst.py
python test2rst.py tutorials/
static/logo-evolve.ico: static/logo-evolve.svg
convert -resize 36x36 static/logo-evolve.svg static/logo-evolve.ico