This PR adds `undef: :replace` option for `CSV.open`.
`File.open` has `undef: :replace` option, but `CSV.open` does not.
It would be convenient if `CSV.open` could have a shortcut by having
`undef: :replace` option.
cff8b18480
This includes performance improvements and backward incompatibility
fixes.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67560 b2dd03c8-39d4-4d8f-98ff-823fe69b080e