Devkit_core.FilesSourceFile system
f fd path rel gets invoked for each file under dirname where fd is a read-only Unix.file_descr, path is full path and rel - path relative to dirname
iter_names_q dirname (fun [path] [rel] -> ...)
iter_files dirname (fun [path] [ic] -> ...)
save_as filename ?mode f is similar to Control.with_open_file_bin except that writing is done to a temporary file that will be renamed to filename after f has succesfully terminated. Therefore this guarantee that either filename will not be modified or will contain whatever f was writing to it as a side-effect.
FIXME windows