# `Exgit.RefName`
[🔗](https://github.com/ivarvong/exgit/blob/v0.1.0/lib/exgit/ref_name.ex#L1)

Validation of git ref names per [`git check-ref-format`][1] rules.

Ref names come from the wire protocol on fetch (`ls-refs` response) and
must be validated **at the transport boundary** before being joined
into any filesystem path. A hostile or compromised server can
advertise a ref name containing `..`, an absolute path, a control
character, or other garbage; without validation, that name would
escape the repository root when used in `Path.join(root, ref)`.

Exgit rejects unsafe names at the transport layer (ls_refs/fetch
return) and never lets them reach the ref store.

## Rules (matching git's C implementation)

* No component may start with `.`
* No component may end with `.lock` or `.`
* No empty component (forbids `//` or leading/trailing `/`)
* No `..` anywhere
* No ASCII control chars (< 0x20), DEL (0x7F)
* No space, `~`, `^`, `:`, `?`, `*`, `[`, `\`, or `@{`
* No bare `@`
* Single-component names are rejected unless they are well-known
  (`HEAD`, `FETCH_HEAD`, `ORIG_HEAD`, `MERGE_HEAD`, `CHERRY_PICK_HEAD`)

[1]: https://git-scm.com/docs/git-check-ref-format

# `valid?`

```elixir
@spec valid?(term()) :: boolean()
```

Return true iff `name` is a safe git ref name.

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*Consult [api-reference.md](api-reference.md) for complete listing*