mise settings add idiomatic_version_file_enable_tools stores duplicates in config

[jdx]

Discussed in https://github.com/jdx/mise/discussions/4918

^{Originally posted by shaicoleman April 23, 2025}

$ mise --version
2025.4.7 linux-x64 (2025-04-23)
$ mise settings add idiomatic_version_file_enable_tools ruby
$ mise settings add idiomatic_version_file_enable_tools ruby
$ cat ~/.config/mise/config.toml
[settings]
idiomatic_version_file_enable_tools = ["ruby", "ruby"]
```</div>