fix: Handle '# [include]'. Update default config

[slowsage]

Default config will now work (with commented out include section).

Standards checklist:

• The PR title is descriptive.
• I have read CONTRIBUTING.md
• The code compiles (cargo build)
• The code passes rustfmt (cargo fmt)
• The code passes clippy (cargo clippy)
• The code passes tests (cargo test)
• Optional: I have tested the code myself
  • I also tested that Topgrade skips the step where needed

If you developed a feature or a bug fix for someone else and you do not have the
means to test it, please tag this person here.

[SteveLauC]

In config.rs, almost every other types take Option<> field, IMHO, it would be better to make struct Include take Option<Vec<String>>, but this needs some extra work to be done as Merge(crate used to handle the file merging logic) does not support merge Option<Vec<T>>

pub struct Include {
    paths: Option<Vec<String>>,
}

@slowsage Would u like to implement this in this PR, if not, leaving it as is is still good enough to me:)

[slowsage]

Vagrant has:

pub struct Vagrant {
    #[merge(strategy = crate::utils::merge_strategies::vec_prepend_opt)]
    directories: Option<Vec<String>>,

    power_on: Option<bool>,
    always_suspend: Option<bool>,
}

I can take a crack if vec_prepend_opt is the way.

[s34m]

Is it ready to be merged?

[SteveLauC]

Is it ready to be merged?

Nope I guess, @slowsage is willing to implement this, and it may take some time:)

[slowsage]

Tested it with paths as optional. Please confirm that I did the unwrap appropriately. Thank you!

[SteveLauC]

LGTM! Thanks