help: do not suggest "update --clean ." to cancel uncommitted merge Follows up 41ef02ba329b.

minifileset: note the unsupported file pattern when raising a parse error This was useful in debugging, because I stupidly quoted it out of habit from the command line. This isn't a great example that clearly shows the problem, but I don't know how to improve it. The problem *is* obvious once a complex statement or a clearly bogus string is used.