ENV.dup returned a plain Object, since all of ENV's behavior is
defined in ENV's singleton class. So using dup makes no sense.
ENV.clone works and is used in some gems, but it doesn't do what
the user expects, since modifying ENV.clone also modifies ENV.
Add a deprecation warning pointing the user to use ENV.to_h
instead.
This also undefines some private initialize* methods in ENV,
since they are not needed.
Added by jeremyevans (Jeremy Evans) about 4 years ago
Make ENV.clone warn and ENV.dup raise
ENV.dup returned a plain Object, since all of ENV's behavior is
defined in ENV's singleton class. So using dup makes no sense.
ENV.clone works and is used in some gems, but it doesn't do what
the user expects, since modifying ENV.clone also modifies ENV.
Add a deprecation warning pointing the user to use ENV.to_h
instead.
This also undefines some private initialize* methods in ENV,
since they are not needed.
Fixes [Bug #17767]