log: move miscellaneous filter/matcher options to walkopts
Maybe this is the most uninteresting patch. I want to remove the dependency
on untyped/unlabeled opts dict at all.
I thought --no-merges and --only-merges could be merged into a single enum
value, but actually they both can be set to filter out everything.
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true