2962 - sketching some literate examples
2963 - no, let's forget naming hunks for now

New plan: only direct hunks into targets; position hunks using selector syntax.
2964
2965

If we're only matching on lines then only 'before' and 'after' make
sense.
2966

tellg/seekg > put_back; works across ifstream/istringstream, and not
brittle about the precise sequence of newline chars read at the end
of line.
2967 - literate before/after directives
2968 - 'wart tangle' command
2969
2970
2971 - 'wart tangle' multiple files