Redo the locking around checkout

Some workers need to do more checkouts, and get confused if two run
simultaneously. Give them the option to tell the main worker not to
unlock the git dir and make them do it themselves.
Switch to latest dagre-d3 and make CSS work again
Don't keep locks after errors
Align status blobs
Turn the svg blobs into links to the relevant sections
Actually reread the correct config
github_docs: Create the gh-pages branch if it does not exist