Is it good to use `reverse_merge!` on the optional hash argument of a method?

I found an example in this guide

```
def obliterate(things, options = {})
default_options = {
:gently => true, # obliterate with soft-delete
:except => [], # skip obliterating these things
:at => Time.now, # don't obliterate them until later
}
options.reverse_merge!(default_options)

...
end
```

I'm wondering whether this is a good practice. When you use this method, the input options hash might be modified by `reverse_merge!` method, which, in my opinion, is very error-prone process in a big project.

Start by locating the guide containing the `obliterate` example and review how optional hash arguments and `reverse_merge!` are discussed. Check the surrounding documentation and any related style guidance; done means the question has a settled recommendation and the guide reflects it clearly.

Written by the indexing model from the issue text.