v3.0.0

git-tidy 3.0.0

Major, because clean means something different now. A directory holding one
protected file used to be moved to quarantine whole — a 400 MB node_modules
renamed into a directory in the same workspace because one file in it was
called tokenizer.js, reclaiming nothing. It is thinned out instead: the
protected entries stay exactly where they are and everything else goes.

Configs that used to be accepted are now refused, all of them cases where the
two YAML parsers disagreed or where the value could only have been a mistake:
a list key with nothing after it, a negative count, a tab outside the
indentation, a flow collection as a mapping key, key:value with no space.

New: doctor --fix, the automatic quarantine expiry, and stopping early when
the network rather than the repository is the problem.