Missing optional scopes

[stratosgear]

Is your feature request related to a problem? Please describe.
I cannot iterate over commits that are missing a scope.

According to the Tera docs of group-by, items that lack an attribute are discarded.

This means that if I want to have a scoped changelog, as per the git-cliff example, (and I do) then these commits are skipped from the changelog.

Describe the solution you'd like
I would like git-cliff to mark these commits in a specially named scope (maybe called unscoped? maybe have it configurable?) so I can iterate over them in my template and create a special section/heading for them

Describe alternatives you've considered
If git-cliff does not somehow mark these missing scopes, I do not believe there is an alternative on iterating over them.

Additional context
Some capture of the output of git-clif when scopes are missing:

# Changelog
All notable changes to this project will be documented in this file.

## [unreleased]

### Documentation

### Infrastructure

#### Ide

- Added git commit hooks for conventional messages
- Added suggested VS Code extensions

<!-- generated by git-cliff -->

Note the Documentation section that does not display any commits there (since the commit message is like docs: some commit message

[orhun]

Hello! Thanks for submitting this. It's implemented in b5df656.

I thought it'd be best to make this configurable via commit_parsers so that a "default" scope can be used for each group:

commit_parsers = [
    { message = "^feat*", group = "Features", default_scope = "general"},
    { message = "^fix*", group = "Bug Fixes", default_scope = "other"},
    { message = "^doc*", group = "Documentation", default_scope = "unscoped"},
]

default_scope will be used if there's no "conventional scope" (in other words: if it's missing). So when you use the config values from above with the following git history:

* docs(config): support multiple file formats
* docs: some commit message

You get the following:

### Documentation

#### Config

- Document values

#### Unscoped

- Some commit message

I think this meets your requirements 😃

default_scope will be available with the next release but feel free to try it out now and report bugs if any.

[stratosgear]

Sure, that would do fine!

Now, all I need is a new release so I can pull the new version in my build image so I can continue automating things. Sagol! :)

[orhun]

v0.3.0 is released.