git-ref-format: Copy over from radicle-git

This is the result of

    cp -r \
      ../radicle-git/radicle-git-ext/git-ref-format/core/src/{{cbor,check,deriv,lit,name,refspec,serde}.rs,{name,refspec}} \
      crates/radicle-git-ref-format/src/

with the radicle-git workspace at commit
8c5df5ecbd3f2507d323608b52e1fbf7b177d864.

crates/radicle-git-ref-format/src/cbor.rs

@@ -0,0 +1,106 @@
+use std::convert::TryFrom;
+
+use minicbor::{
+    decode,
+    encode::{self, Write},
+    Decode, Decoder, Encode, Encoder,
+};
+
+use crate::{
+    refspec::{PatternStr, PatternString},
+    Namespaced, Qualified, RefStr, RefString,
+};
+
+impl<'de: 'a, 'a> Decode<'de> for &'a RefStr {
+    #[inline]
+    fn decode(d: &mut Decoder<'de>) -> Result<Self, decode::Error> {
+        d.str()
+            .and_then(|s| Self::try_from(s).map_err(|e| decode::Error::Custom(Box::new(e))))
+    }
+}
+
+impl Encode for &RefStr {
+    #[inline]
+    fn encode<W: Write>(&self, e: &mut Encoder<W>) -> Result<(), encode::Error<W::Error>> {
+        e.str(self.as_str())?;
+        Ok(())
+    }
+}
+
+impl<'de> Decode<'de> for RefString {
+    #[inline]
+    fn decode(d: &mut Decoder<'de>) -> Result<Self, decode::Error> {
+        Decode::decode(d).map(|s: &RefStr| s.to_owned())
+    }
+}
+
+impl Encode for RefString {
+    #[inline]
+    fn encode<W: Write>(&self, e: &mut Encoder<W>) -> Result<(), encode::Error<W::Error>> {
+        self.as_refstr().encode(e)
+    }
+}
+
+impl<'de: 'a, 'a> Decode<'de> for &'a PatternStr {
+    #[inline]
+    fn decode(d: &mut Decoder<'de>) -> Result<Self, decode::Error> {
+        d.str()
+            .and_then(|s| Self::try_from(s).map_err(|e| decode::Error::Custom(Box::new(e))))
+    }
+}
+
+impl Encode for &PatternStr {
+    #[inline]
+    fn encode<W: Write>(&self, e: &mut Encoder<W>) -> Result<(), encode::Error<W::Error>> {
+        e.str(self.as_str())?;
+        Ok(())
+    }
+}
+
+impl<'de> Decode<'de> for PatternString {
+    #[inline]
+    fn decode(d: &mut Decoder<'de>) -> Result<Self, decode::Error> {
+        Decode::decode(d).map(|s: &PatternStr| s.to_owned())
+    }
+}
+
+impl Encode for PatternString {
+    #[inline]
+    fn encode<W: Write>(&self, e: &mut Encoder<W>) -> Result<(), encode::Error<W::Error>> {
+        self.as_pattern_str().encode(e)
+    }
+}
+
+impl<'de: 'a, 'a> Decode<'de> for Qualified<'a> {
+    #[inline]
+    fn decode(d: &mut Decoder<'de>) -> Result<Self, decode::Error> {
+        Decode::decode(d).and_then(|s: &RefStr| {
+            s.qualified()
+                .ok_or(decode::Error::Message("not a qualified ref"))
+        })
+    }
+}
+
+impl Encode for Qualified<'_> {
+    #[inline]
+    fn encode<W: Write>(&self, e: &mut Encoder<W>) -> Result<(), encode::Error<W::Error>> {
+        self.as_str().encode(e)
+    }
+}
+
+impl<'de: 'a, 'a> Decode<'de> for Namespaced<'a> {
+    #[inline]
+    fn decode(d: &mut Decoder<'de>) -> Result<Self, decode::Error> {
+        Decode::decode(d).and_then(|s: &RefStr| {
+            s.to_namespaced()
+                .ok_or(decode::Error::Message("not a namespaced ref"))
+        })
+    }
+}
+
+impl Encode for Namespaced<'_> {
+    #[inline]
+    fn encode<W: Write>(&self, e: &mut Encoder<W>) -> Result<(), encode::Error<W::Error>> {
+        self.as_str().encode(e)
+    }
+}

crates/radicle-git-ref-format/src/check.rs

@@ -0,0 +1,101 @@
+use thiserror::Error;
+
+pub struct Options {
+    /// If `false`, the refname must contain at least one `/`.
+    pub allow_onelevel: bool,
+    /// If `true`, the refname may contain exactly one `*` character.
+    pub allow_pattern: bool,
+}
+
+#[derive(Debug, PartialEq, Eq, Error)]
+#[non_exhaustive]
+pub enum Error {
+    #[error("empty input")]
+    Empty,
+    #[error("lone '@' character")]
+    LoneAt,
+    #[error("consecutive or trailing slash")]
+    Slash,
+    #[error("ends with '.lock'")]
+    DotLock,
+    #[error("consecutive dots ('..')")]
+    DotDot,
+    #[error("at-open-brace ('@{{')")]
+    AtOpenBrace,
+    #[error("invalid character {0:?}")]
+    InvalidChar(char),
+    #[error("component starts with '.'")]
+    StartsDot,
+    #[error("component ends with '.'")]
+    EndsDot,
+    #[error("control character")]
+    Control,
+    #[error("whitespace")]
+    Space,
+    #[error("must contain at most one '*'")]
+    Pattern,
+    #[error("must contain at least one '/'")]
+    OneLevel,
+}
+
+/// Validate that a string slice is a valid refname.
+pub fn ref_format(opts: Options, s: &str) -> Result<(), Error> {
+    match s {
+        "" => Err(Error::Empty),
+        "@" => Err(Error::LoneAt),
+        "." => Err(Error::StartsDot),
+        _ => {
+            let mut globs = 0usize;
+            let mut parts = 0usize;
+
+            for x in s.split('/') {
+                if x.is_empty() {
+                    return Err(Error::Slash);
+                }
+
+                parts += 1;
+
+                if x.ends_with(".lock") {
+                    return Err(Error::DotLock);
+                }
+
+                let last_char = x.chars().count() - 1;
+                for (i, y) in x.chars().zip(x.chars().cycle().skip(1)).enumerate() {
+                    match y {
+                        ('.', '.') => return Err(Error::DotDot),
+                        ('@', '{') => return Err(Error::AtOpenBrace),
+
+                        ('\0', _) => return Err(Error::InvalidChar('\0')),
+                        ('\\', _) => return Err(Error::InvalidChar('\\')),
+                        ('~', _) => return Err(Error::InvalidChar('~')),
+                        ('^', _) => return Err(Error::InvalidChar('^')),
+                        (':', _) => return Err(Error::InvalidChar(':')),
+                        ('?', _) => return Err(Error::InvalidChar('?')),
+                        ('[', _) => return Err(Error::InvalidChar('[')),
+
+                        ('*', _) => globs += 1,
+
+                        ('.', _) if i == 0 => return Err(Error::StartsDot),
+                        ('.', _) if i == last_char => return Err(Error::EndsDot),
+
+                        (' ', _) => return Err(Error::Space),
+
+                        (z, _) if z.is_ascii_control() => return Err(Error::Control),
+
+                        _ => continue,
+                    }
+                }
+            }
+
+            if parts < 2 && !opts.allow_onelevel {
+                Err(Error::OneLevel)
+            } else if globs > 1 && opts.allow_pattern {
+                Err(Error::Pattern)
+            } else if globs > 0 && !opts.allow_pattern {
+                Err(Error::InvalidChar('*'))
+            } else {
+                Ok(())
+            }
+        }
+    }
+}

crates/radicle-git-ref-format/src/deriv.rs

@@ -0,0 +1,397 @@
+use std::{
+    borrow::Cow,
+    fmt::{self, Display},
+    ops::Deref,
+};
+
+use crate::{
+    lit, name,
+    refspec::{PatternStr, QualifiedPattern},
+    Component, RefStr, RefString,
+};
+
+/// A fully-qualified refname.
+///
+/// A refname is qualified _iff_ it starts with "refs/" and has at least three
+/// components. This implies that a [`Qualified`] ref has a category, such as
+/// "refs/heads/main".
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Qualified<'a>(pub(crate) Cow<'a, RefStr>);
+
+impl<'a> Qualified<'a> {
+    /// Infallibly create a [`Qualified`] from components.
+    ///
+    /// Note that the "refs/" prefix is implicitly added, so `a` is the second
+    /// [`Component`]. Mirroring [`Self::non_empty_components`], providing
+    /// two [`Component`]s guarantees well-formedness of the [`Qualified`].
+    /// `tail` may be empty.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use git_ref_format::{component, Qualified};
+    ///
+    /// assert_eq!(
+    ///     "refs/heads/main",
+    ///     Qualified::from_components(component::HEADS, component::MAIN, None).as_str()
+    /// )
+    /// ```
+    pub fn from_components<'b, 'c, 'd, A, B, C>(a: A, b: B, tail: C) -> Self
+    where
+        A: Into<Component<'b>>,
+        B: Into<Component<'c>>,
+        C: IntoIterator<Item = Component<'d>>,
+    {
+        let mut inner = name::REFS.join(a.into()).and(b.into());
+        inner.extend(tail);
+
+        Self(inner.into())
+    }
+
+    pub fn from_refstr(r: impl Into<Cow<'a, RefStr>>) -> Option<Self> {
+        Self::_from_refstr(r.into())
+    }
+
+    fn _from_refstr(r: Cow<'a, RefStr>) -> Option<Self> {
+        let mut iter = r.iter();
+        match (iter.next()?, iter.next()?, iter.next()?) {
+            ("refs", _, _) => Some(Qualified(r)),
+            _ => None,
+        }
+    }
+
+    #[inline]
+    pub fn as_str(&self) -> &str {
+        self.as_ref()
+    }
+
+    #[inline]
+    pub fn join<'b, R>(&self, other: R) -> Qualified<'b>
+    where
+        R: AsRef<RefStr>,
+    {
+        Qualified(self.0.join(other).into())
+    }
+
+    pub fn to_pattern<P>(&'a self, pattern: P) -> QualifiedPattern<'a>
+    where
+        P: AsRef<PatternStr>,
+    {
+        QualifiedPattern(Cow::Owned(RefStr::to_pattern(self, pattern.as_ref())))
+    }
+
+    #[inline]
+    pub fn to_namespaced(&'a self) -> Option<Namespaced<'a>> {
+        self.0.as_ref().into()
+    }
+
+    /// Add a namespace.
+    ///
+    /// Creates a new [`Namespaced`] by prefxing `self` with
+    /// `refs/namespaces/<ns>`.
+    pub fn with_namespace<'b>(&self, ns: Component<'b>) -> Namespaced<'a> {
+        Namespaced(Cow::Owned(
+            IntoIterator::into_iter([lit::Refs.into(), lit::Namespaces.into(), ns])
+                .chain(self.0.components())
+                .collect(),
+        ))
+    }
+
+    /// Like [`Self::non_empty_components`], but with string slices.
+    pub fn non_empty_iter(&'a self) -> (&'a str, &'a str, &'a str, name::Iter<'a>) {
+        let mut iter = self.iter();
+        (
+            iter.next().unwrap(),
+            iter.next().unwrap(),
+            iter.next().unwrap(),
+            iter,
+        )
+    }
+
+    /// Return the first three [`Component`]s, and a possibly empty iterator
+    /// over the remaining ones.
+    ///
+    /// A qualified ref is guaranteed to have at least three components, which
+    /// this method provides a witness of. This is useful eg. for pattern
+    /// matching on the prefix.
+    pub fn non_empty_components(
+        &'a self,
+    ) -> (
+        Component<'a>,
+        Component<'a>,
+        Component<'a>,
+        name::Components<'a>,
+    ) {
+        let mut cs = self.components();
+        (
+            cs.next().unwrap(),
+            cs.next().unwrap(),
+            cs.next().unwrap(),
+            cs,
+        )
+    }
+
+    #[inline]
+    pub fn to_owned<'b>(&self) -> Qualified<'b> {
+        Qualified(Cow::Owned(self.0.clone().into_owned()))
+    }
+
+    #[inline]
+    pub fn into_owned<'b>(self) -> Qualified<'b> {
+        Qualified(Cow::Owned(self.0.into_owned()))
+    }
+
+    #[inline]
+    pub fn into_refstring(self) -> RefString {
+        self.into()
+    }
+}
+
+impl Deref for Qualified<'_> {
+    type Target = RefStr;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<RefStr> for Qualified<'_> {
+    #[inline]
+    fn as_ref(&self) -> &RefStr {
+        self
+    }
+}
+
+impl AsRef<str> for Qualified<'_> {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+impl AsRef<Self> for Qualified<'_> {
+    #[inline]
+    fn as_ref(&self) -> &Self {
+        self
+    }
+}
+
+impl<'a> From<Qualified<'a>> for Cow<'a, RefStr> {
+    #[inline]
+    fn from(q: Qualified<'a>) -> Self {
+        q.0
+    }
+}
+
+impl From<Qualified<'_>> for RefString {
+    #[inline]
+    fn from(q: Qualified) -> Self {
+        q.0.into_owned()
+    }
+}
+
+impl<T, U> From<(lit::Refs, T, U)> for Qualified<'_>
+where
+    T: AsRef<RefStr>,
+    U: AsRef<RefStr>,
+{
+    #[inline]
+    fn from((refs, cat, name): (lit::Refs, T, U)) -> Self {
+        let refs: &RefStr = refs.into();
+        Self(Cow::Owned(refs.join(cat).and(name)))
+    }
+}
+
+impl<T> From<lit::RefsHeads<T>> for Qualified<'_>
+where
+    T: AsRef<RefStr>,
+{
+    #[inline]
+    fn from((refs, heads, name): lit::RefsHeads<T>) -> Self {
+        Self(Cow::Owned(
+            IntoIterator::into_iter([Component::from(refs), heads.into()])
+                .collect::<RefString>()
+                .and(name),
+        ))
+    }
+}
+
+impl<T> From<lit::RefsTags<T>> for Qualified<'_>
+where
+    T: AsRef<RefStr>,
+{
+    #[inline]
+    fn from((refs, tags, name): lit::RefsTags<T>) -> Self {
+        Self(Cow::Owned(
+            IntoIterator::into_iter([Component::from(refs), tags.into()])
+                .collect::<RefString>()
+                .and(name),
+        ))
+    }
+}
+
+impl<T> From<lit::RefsNotes<T>> for Qualified<'_>
+where
+    T: AsRef<RefStr>,
+{
+    #[inline]
+    fn from((refs, notes, name): lit::RefsNotes<T>) -> Self {
+        Self(Cow::Owned(
+            IntoIterator::into_iter([Component::from(refs), notes.into()])
+                .collect::<RefString>()
+                .and(name),
+        ))
+    }
+}
+
+impl<T> From<lit::RefsRemotes<T>> for Qualified<'_>
+where
+    T: AsRef<RefStr>,
+{
+    #[inline]
+    fn from((refs, remotes, name): lit::RefsRemotes<T>) -> Self {
+        Self(Cow::Owned(
+            IntoIterator::into_iter([Component::from(refs), remotes.into()])
+                .collect::<RefString>()
+                .and(name),
+        ))
+    }
+}
+
+impl Display for Qualified<'_> {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+/// A [`Qualified`] ref under a git namespace.
+///
+/// A ref is namespaced if it starts with "refs/namespaces/", another path
+/// component, and "refs" or "HEAD". Eg.
+///
+///     refs/namespaces/xyz/refs/heads/main
+///     refs/namespaces/xyz/HEAD
+///
+/// Note that namespaces can be nested, so the result of
+/// [`Namespaced::strip_namespace`] may be convertible to a [`Namespaced`]
+/// again. For example:
+///
+/// ```no_run
+/// let full = refname!("refs/namespaces/a/refs/namespaces/b/refs/heads/main");
+/// let namespaced = full.namespaced().unwrap();
+/// let strip_first = namespaced.strip_namespace();
+/// let nested = strip_first.namespaced().unwrap();
+/// let strip_second = nested.strip_namespace();
+///
+/// assert_eq!("a", namespaced.namespace().as_str());
+/// assert_eq!("b", nested.namespace().as_str());
+/// assert_eq!("refs/namespaces/b/refs/heads/main", strip_first.as_str());
+/// assert_eq!("refs/heads/main", strip_second.as_str());
+/// ```
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Namespaced<'a>(Cow<'a, RefStr>);
+
+impl<'a> Namespaced<'a> {
+    pub fn namespace(&'a self) -> Component<'a> {
+        self.components().nth(2).unwrap()
+    }
+
+    pub fn strip_namespace<'b>(&self) -> Qualified<'b> {
+        const REFS_NAMESPACES: &RefStr = RefStr::from_str("refs/namespaces");
+
+        Qualified(Cow::Owned(
+            self.strip_prefix(REFS_NAMESPACES)
+                .unwrap()
+                .components()
+                .skip(1)
+                .collect(),
+        ))
+    }
+
+    pub fn strip_namespace_recursive<'b>(&self) -> Qualified<'b> {
+        let mut strip = self.strip_namespace();
+        while let Some(ns) = strip.to_namespaced() {
+            strip = ns.strip_namespace();
+        }
+        strip
+    }
+
+    #[inline]
+    pub fn to_owned<'b>(&self) -> Namespaced<'b> {
+        Namespaced(Cow::Owned(self.0.clone().into_owned()))
+    }
+
+    #[inline]
+    pub fn into_owned<'b>(self) -> Namespaced<'b> {
+        Namespaced(Cow::Owned(self.0.into_owned()))
+    }
+
+    #[inline]
+    pub fn into_qualified(self) -> Qualified<'a> {
+        self.into()
+    }
+}
+
+impl Deref for Namespaced<'_> {
+    type Target = RefStr;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<RefStr> for Namespaced<'_> {
+    #[inline]
+    fn as_ref(&self) -> &RefStr {
+        self
+    }
+}
+
+impl AsRef<str> for Namespaced<'_> {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+impl<'a> From<Namespaced<'a>> for Qualified<'a> {
+    #[inline]
+    fn from(ns: Namespaced<'a>) -> Self {
+        Self(ns.0)
+    }
+}
+
+impl<'a> From<&'a RefStr> for Option<Namespaced<'a>> {
+    fn from(rs: &'a RefStr) -> Self {
+        let mut cs = rs.iter();
+        match (cs.next()?, cs.next()?, cs.next()?, cs.next()?) {
+            ("refs", "namespaces", _, "refs" | "HEAD") => Some(Namespaced(Cow::from(rs))),
+
+            _ => None,
+        }
+    }
+}
+
+impl<'a, T> From<lit::RefsNamespaces<'_, T>> for Namespaced<'static>
+where
+    T: Into<Component<'a>>,
+{
+    #[inline]
+    fn from((refs, namespaces, namespace, name): lit::RefsNamespaces<T>) -> Self {
+        Self(Cow::Owned(
+            IntoIterator::into_iter([refs.into(), namespaces.into(), namespace.into()])
+                .collect::<RefString>()
+                .and(name),
+        ))
+    }
+}
+
+impl Display for Namespaced<'_> {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}

crates/radicle-git-ref-format/src/lit.rs

@@ -0,0 +1,192 @@
+use crate::{name, Qualified, RefStr};
+
+/// A literal [`RefStr`].
+///
+/// Types implementing [`Lit`] must be [`name::Component`]s, and provide a
+/// conversion from a component _iff_ the component's [`RefStr`] representation
+/// is equal to [`Lit::NAME`]. Because these morphisms can only be guaranteed
+/// axiomatically, the trait can not currently be implemented by types outside
+/// of this crate.
+///
+/// [`Lit`] types are useful for efficiently creating known-valid [`Qualified`]
+/// refs, and sometimes for pattern matching.
+pub trait Lit: Sized + sealed::Sealed {
+    const SELF: Self;
+    const NAME: &'static RefStr;
+
+    #[inline]
+    fn from_component(c: &name::Component) -> Option<Self> {
+        (c.as_ref() == Self::NAME).then_some(Self::SELF)
+    }
+}
+
+impl<T: Lit> From<T> for &'static RefStr {
+    #[inline]
+    fn from(_: T) -> Self {
+        T::NAME
+    }
+}
+
+mod sealed {
+    pub trait Sealed {}
+}
+
+/// All known literal [`RefStr`]s.
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub enum KnownLit {
+    Refs,
+    Heads,
+    Namespaces,
+    Remotes,
+    Tags,
+    Notes,
+}
+
+impl KnownLit {
+    #[inline]
+    pub fn from_component(c: &name::Component) -> Option<Self> {
+        let c: &RefStr = c.as_ref();
+        if c == Refs::NAME {
+            Some(Self::Refs)
+        } else if c == Heads::NAME {
+            Some(Self::Heads)
+        } else if c == Namespaces::NAME {
+            Some(Self::Namespaces)
+        } else if c == Remotes::NAME {
+            Some(Self::Remotes)
+        } else if c == Tags::NAME {
+            Some(Self::Tags)
+        } else if c == Notes::NAME {
+            Some(Self::Notes)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<KnownLit> for name::Component<'_> {
+    #[inline]
+    fn from(k: KnownLit) -> Self {
+        match k {
+            KnownLit::Refs => Refs.into(),
+            KnownLit::Heads => Heads.into(),
+            KnownLit::Namespaces => Namespaces.into(),
+            KnownLit::Remotes => Remotes.into(),
+            KnownLit::Tags => Tags.into(),
+            KnownLit::Notes => Notes.into(),
+        }
+    }
+}
+
+/// Either a [`KnownLit`] or a [`name::Component`]
+pub enum SomeLit<'a> {
+    Known(KnownLit),
+    Any(name::Component<'a>),
+}
+
+impl SomeLit<'_> {
+    pub fn known(self) -> Option<KnownLit> {
+        match self {
+            Self::Known(k) => Some(k),
+            _ => None,
+        }
+    }
+}
+
+impl<'a> From<name::Component<'a>> for SomeLit<'a> {
+    #[inline]
+    fn from(c: name::Component<'a>) -> Self {
+        match KnownLit::from_component(&c) {
+            Some(k) => Self::Known(k),
+            None => Self::Any(c),
+        }
+    }
+}
+
+pub type RefsHeads<T> = (Refs, Heads, T);
+pub type RefsTags<T> = (Refs, Tags, T);
+pub type RefsNotes<T> = (Refs, Notes, T);
+pub type RefsRemotes<T> = (Refs, Remotes, T);
+pub type RefsNamespaces<'a, T> = (Refs, Namespaces, T, Qualified<'a>);
+
+#[inline]
+pub fn refs_heads<T: AsRef<RefStr>>(name: T) -> RefsHeads<T> {
+    (Refs, Heads, name)
+}
+
+#[inline]
+pub fn refs_tags<T: AsRef<RefStr>>(name: T) -> RefsTags<T> {
+    (Refs, Tags, name)
+}
+
+#[inline]
+pub fn refs_notes<T: AsRef<RefStr>>(name: T) -> RefsNotes<T> {
+    (Refs, Notes, name)
+}
+
+#[inline]
+pub fn refs_remotes<T: AsRef<RefStr>>(name: T) -> RefsRemotes<T> {
+    (Refs, Remotes, name)
+}
+
+#[inline]
+pub fn refs_namespaces<'a, 'b, T>(namespace: T, name: Qualified<'b>) -> RefsNamespaces<'b, T>
+where
+    T: Into<name::Component<'a>>,
+{
+    (Refs, Namespaces, namespace, name)
+}
+
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Refs;
+
+impl Lit for Refs {
+    const SELF: Self = Self;
+    const NAME: &'static RefStr = name::REFS;
+}
+impl sealed::Sealed for Refs {}
+
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Heads;
+
+impl Lit for Heads {
+    const SELF: Self = Self;
+    const NAME: &'static RefStr = name::HEADS;
+}
+impl sealed::Sealed for Heads {}
+
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Namespaces;
+
+impl Lit for Namespaces {
+    const SELF: Self = Self;
+    const NAME: &'static RefStr = name::NAMESPACES;
+}
+impl sealed::Sealed for Namespaces {}
+
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Remotes;
+
+impl Lit for Remotes {
+    const SELF: Self = Self;
+    const NAME: &'static RefStr = name::REMOTES;
+}
+impl sealed::Sealed for Remotes {}
+
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Tags;
+
+impl Lit for Tags {
+    const SELF: Self = Self;
+    const NAME: &'static RefStr = name::TAGS;
+}
+impl sealed::Sealed for Tags {}
+
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Notes;
+
+impl Lit for Notes {
+    const SELF: Self = Self;
+    const NAME: &'static RefStr = name::NOTES;
+}
+impl sealed::Sealed for Notes {}

crates/radicle-git-ref-format/src/name.rs

@@ -0,0 +1,464 @@
+use std::{
+    borrow::{Borrow, Cow},
+    convert::TryFrom,
+    fmt::{self, Display},
+    iter::{Extend, FromIterator},
+    ops::Deref,
+};
+
+use crate::{
+    check,
+    refspec::{PatternStr, PatternString},
+    Namespaced, Qualified,
+};
+
+mod iter;
+pub use iter::{component, Component, Components, Iter};
+
+#[cfg(feature = "percent-encoding")]
+pub use percent_encoding::PercentEncode;
+
+pub const HEADS: &RefStr = RefStr::from_str(str::HEADS);
+pub const MAIN: &RefStr = RefStr::from_str(str::MAIN);
+pub const MASTER: &RefStr = RefStr::from_str(str::MASTER);
+pub const NAMESPACES: &RefStr = RefStr::from_str(str::NAMESPACES);
+pub const NOTES: &RefStr = RefStr::from_str(str::NOTES);
+pub const ORIGIN: &RefStr = RefStr::from_str(str::ORIGIN);
+pub const REFS: &RefStr = RefStr::from_str(str::REFS);
+pub const REMOTES: &RefStr = RefStr::from_str(str::REMOTES);
+pub const TAGS: &RefStr = RefStr::from_str(str::TAGS);
+
+pub const REFS_HEADS_MAIN: &RefStr = RefStr::from_str(str::REFS_HEADS_MAIN);
+pub const REFS_HEADS_MASTER: &RefStr = RefStr::from_str(str::REFS_HEADS_MASTER);
+
+pub mod str {
+    pub const HEADS: &str = "heads";
+    pub const MAIN: &str = "main";
+    pub const MASTER: &str = "master";
+    pub const NAMESPACES: &str = "namespaces";
+    pub const NOTES: &str = "notes";
+    pub const ORIGIN: &str = "origin";
+    pub const REFS: &str = "refs";
+    pub const REMOTES: &str = "remotes";
+    pub const TAGS: &str = "tags";
+
+    pub const REFS_HEADS_MAIN: &str = "refs/heads/main";
+    pub const REFS_HEADS_MASTER: &str = "refs/heads/master";
+}
+
+pub mod bytes {
+    use super::str;
+
+    pub const HEADS: &[u8] = str::HEADS.as_bytes();
+    pub const MAIN: &[u8] = str::MAIN.as_bytes();
+    pub const MASTER: &[u8] = str::MASTER.as_bytes();
+    pub const NAMESPACES: &[u8] = str::NAMESPACES.as_bytes();
+    pub const NOTES: &[u8] = str::NOTES.as_bytes();
+    pub const ORIGIN: &[u8] = str::ORIGIN.as_bytes();
+    pub const REFS: &[u8] = str::REFS.as_bytes();
+    pub const REMOTES: &[u8] = str::REMOTES.as_bytes();
+    pub const TAGS: &[u8] = str::TAGS.as_bytes();
+
+    pub const REFS_HEADS_MAIN: &[u8] = str::REFS_HEADS_MAIN.as_bytes();
+    pub const REFS_HEADS_MASTER: &[u8] = str::REFS_HEADS_MASTER.as_bytes();
+}
+
+const CHECK_OPTS: check::Options = check::Options {
+    allow_pattern: false,
+    allow_onelevel: true,
+};
+
+#[repr(transparent)]
+#[derive(Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct RefStr(str);
+
+impl RefStr {
+    pub fn try_from_str(s: &str) -> Result<&RefStr, check::Error> {
+        TryFrom::try_from(s)
+    }
+
+    #[inline]
+    pub fn as_str(&self) -> &str {
+        self
+    }
+
+    #[inline]
+    pub fn to_ref_string(&self) -> RefString {
+        self.to_owned()
+    }
+
+    pub fn strip_prefix<P>(&self, base: P) -> Option<&RefStr>
+    where
+        P: AsRef<RefStr>,
+    {
+        self._strip_prefix(base.as_ref())
+    }
+
+    fn _strip_prefix(&self, base: &RefStr) -> Option<&RefStr> {
+        self.0
+            .strip_prefix(base.as_str())
+            .and_then(|s| s.strip_prefix('/'))
+            .map(Self::from_str)
+    }
+
+    /// Join `other` onto `self`, yielding a new [`RefString`].
+    ///
+    /// Consider to use [`RefString::and`] when chaining multiple fragments
+    /// together, and the intermediate values are not needed.
+    pub fn join<R>(&self, other: R) -> RefString
+    where
+        R: AsRef<RefStr>,
+    {
+        self._join(other.as_ref())
+    }
+
+    fn _join(&self, other: &RefStr) -> RefString {
+        let mut buf = self.to_ref_string();
+        buf.push(other);
+        buf
+    }
+
+    pub fn to_pattern<P>(&self, pattern: P) -> PatternString
+    where
+        P: AsRef<PatternStr>,
+    {
+        self._to_pattern(pattern.as_ref())
+    }
+
+    fn _to_pattern(&self, pattern: &PatternStr) -> PatternString {
+        self.to_owned().with_pattern(pattern)
+    }
+
+    #[inline]
+    pub fn qualified<'a>(&'a self) -> Option<Qualified<'a>> {
+        Qualified::from_refstr(self)
+    }
+
+    #[inline]
+    pub fn to_namespaced<'a>(&'a self) -> Option<Namespaced<'a>> {
+        self.into()
+    }
+
+    pub fn iter<'a>(&'a self) -> Iter<'a> {
+        self.0.split('/')
+    }
+
+    pub fn components<'a>(&'a self) -> Components<'a> {
+        Components::from(self)
+    }
+
+    pub fn head<'a>(&'a self) -> Component<'a> {
+        self.components().next().expect("`RefStr` cannot be empty")
+    }
+
+    #[cfg(feature = "percent-encoding")]
+    pub fn percent_encode(&self) -> PercentEncode {
+        /// https://url.spec.whatwg.org/#fragment-percent-encode-set
+        const FRAGMENT_PERCENT_ENCODE_SET: &percent_encoding::AsciiSet =
+            &percent_encoding::CONTROLS
+                .add(b' ')
+                .add(b'"')
+                .add(b'<')
+                .add(b'>')
+                .add(b'`');
+
+        /// https://url.spec.whatwg.org/#path-percent-encode-set
+        const PATH_PERCENT_ENCODE_SET: &percent_encoding::AsciiSet = &FRAGMENT_PERCENT_ENCODE_SET
+            .add(b'#')
+            .add(b'?')
+            .add(b'{')
+            .add(b'}');
+
+        percent_encoding::utf8_percent_encode(self.as_str(), PATH_PERCENT_ENCODE_SET)
+    }
+
+    #[cfg(feature = "bstr")]
+    #[inline]
+    pub fn as_bstr(&self) -> &bstr::BStr {
+        self.as_ref()
+    }
+
+    pub(crate) const fn from_str(s: &str) -> &RefStr {
+        unsafe { &*(s as *const str as *const RefStr) }
+    }
+}
+
+impl Deref for RefStr {
+    type Target = str;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<str> for RefStr {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self
+    }
+}
+
+#[cfg(feature = "bstr")]
+impl AsRef<bstr::BStr> for RefStr {
+    #[inline]
+    fn as_ref(&self) -> &bstr::BStr {
+        use bstr::ByteSlice as _;
+        self.as_str().as_bytes().as_bstr()
+    }
+}
+
+impl AsRef<RefStr> for &RefStr {
+    #[inline]
+    fn as_ref(&self) -> &RefStr {
+        self
+    }
+}
+
+impl<'a> TryFrom<&'a str> for &'a RefStr {
+    type Error = check::Error;
+
+    #[inline]
+    fn try_from(s: &'a str) -> Result<Self, Self::Error> {
+        check::ref_format(CHECK_OPTS, s).map(|()| RefStr::from_str(s))
+    }
+}
+
+impl<'a> From<&'a RefStr> for Cow<'a, RefStr> {
+    #[inline]
+    fn from(rs: &'a RefStr) -> Cow<'a, RefStr> {
+        Cow::Borrowed(rs)
+    }
+}
+
+impl Display for RefStr {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(self)
+    }
+}
+
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct RefString(String);
+
+impl RefString {
+    #[inline]
+    pub fn as_refstr(&self) -> &RefStr {
+        self
+    }
+
+    /// Join `other` onto `self` in place.
+    ///
+    /// This is a consuming version of [`RefString::push`] which can be chained.
+    /// Prefer this over chaining calls to [`RefStr::join`] if the
+    /// intermediate values are not needed.
+    pub fn and<R>(self, other: R) -> Self
+    where
+        R: AsRef<RefStr>,
+    {
+        self._and(other.as_ref())
+    }
+
+    fn _and(mut self, other: &RefStr) -> Self {
+        self.push(other);
+        self
+    }
+
+    pub fn push<R>(&mut self, other: R)
+    where
+        R: AsRef<RefStr>,
+    {
+        self.0.push('/');
+        self.0.push_str(other.as_ref().as_str());
+    }
+
+    #[inline]
+    pub fn pop(&mut self) -> bool {
+        match self.0.rfind('/') {
+            None => false,
+            Some(idx) => {
+                self.0.truncate(idx);
+                true
+            }
+        }
+    }
+
+    /// Append a [`PatternStr`], turning self into a new [`PatternString`].
+    pub fn with_pattern<P>(self, pattern: P) -> PatternString
+    where
+        P: AsRef<PatternStr>,
+    {
+        self._with_pattern(pattern.as_ref())
+    }
+
+    fn _with_pattern(self, pattern: &PatternStr) -> PatternString {
+        let mut buf = self.0;
+        buf.push('/');
+        buf.push_str(pattern.as_str());
+
+        PatternString(buf)
+    }
+
+    #[inline]
+    pub fn into_qualified<'a>(self) -> Option<Qualified<'a>> {
+        Qualified::from_refstr(self)
+    }
+
+    #[inline]
+    pub fn reserve(&mut self, additional: usize) {
+        self.0.reserve(additional)
+    }
+
+    #[inline]
+    pub fn shrink_to_fit(&mut self) {
+        self.0.shrink_to_fit()
+    }
+
+    #[cfg(feature = "bstr")]
+    #[inline]
+    pub fn into_bstring(self) -> bstr::BString {
+        self.into()
+    }
+
+    #[cfg(feature = "bstr")]
+    #[inline]
+    pub fn as_bstr(&self) -> &bstr::BStr {
+        self.as_ref()
+    }
+}
+
+impl Deref for RefString {
+    type Target = RefStr;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        self.borrow()
+    }
+}
+
+impl AsRef<RefStr> for RefString {
+    #[inline]
+    fn as_ref(&self) -> &RefStr {
+        self
+    }
+}
+
+impl AsRef<str> for RefString {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+#[cfg(feature = "bstr")]
+impl AsRef<bstr::BStr> for RefString {
+    #[inline]
+    fn as_ref(&self) -> &bstr::BStr {
+        use bstr::ByteSlice as _;
+        self.as_str().as_bytes().as_bstr()
+    }
+}
+
+impl Borrow<RefStr> for RefString {
+    #[inline]
+    fn borrow(&self) -> &RefStr {
+        RefStr::from_str(self.0.as_str())
+    }
+}
+
+impl ToOwned for RefStr {
+    type Owned = RefString;
+
+    #[inline]
+    fn to_owned(&self) -> Self::Owned {
+        RefString(self.0.to_owned())
+    }
+}
+
+impl TryFrom<&str> for RefString {
+    type Error = check::Error;
+
+    #[inline]
+    fn try_from(s: &str) -> Result<Self, Self::Error> {
+        RefStr::try_from_str(s).map(ToOwned::to_owned)
+    }
+}
+
+impl TryFrom<String> for RefString {
+    type Error = check::Error;
+
+    #[inline]
+    fn try_from(s: String) -> Result<Self, Self::Error> {
+        check::ref_format(CHECK_OPTS, s.as_str()).map(|()| RefString(s))
+    }
+}
+
+impl<'a> From<&'a RefString> for Cow<'a, RefStr> {
+    #[inline]
+    fn from(rs: &'a RefString) -> Cow<'a, RefStr> {
+        Cow::Borrowed(rs.as_refstr())
+    }
+}
+
+impl<'a> From<RefString> for Cow<'a, RefStr> {
+    #[inline]
+    fn from(rs: RefString) -> Cow<'a, RefStr> {
+        Cow::Owned(rs)
+    }
+}
+
+impl From<RefString> for String {
+    #[inline]
+    fn from(rs: RefString) -> Self {
+        rs.0
+    }
+}
+
+#[cfg(feature = "bstr")]
+impl From<RefString> for bstr::BString {
+    #[inline]
+    fn from(rs: RefString) -> Self {
+        bstr::BString::from(rs.0.into_bytes())
+    }
+}
+
+impl Display for RefString {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+impl<A> FromIterator<A> for RefString
+where
+    A: AsRef<RefStr>,
+{
+    fn from_iter<T>(iter: T) -> Self
+    where
+        T: IntoIterator<Item = A>,
+    {
+        let mut buf = String::new();
+        for c in iter {
+            buf.push_str(c.as_ref().as_str());
+            buf.push('/');
+        }
+        assert!(!buf.is_empty(), "empty iterator");
+        buf.truncate(buf.len() - 1);
+
+        Self(buf)
+    }
+}
+
+impl<A> Extend<A> for RefString
+where
+    A: AsRef<RefStr>,
+{
+    fn extend<T>(&mut self, iter: T)
+    where
+        T: IntoIterator<Item = A>,
+    {
+        for x in iter {
+            self.push(x)
+        }
+    }
+}

crates/radicle-git-ref-format/src/name/iter.rs

@@ -0,0 +1,155 @@
+use std::{
+    borrow::Cow,
+    fmt::{self, Display},
+    ops::Deref,
+};
+
+use super::RefStr;
+use crate::lit;
+
+pub type Iter<'a> = std::str::Split<'a, char>;
+
+/// Iterator created by the [`RefStr::iter`] method.
+#[must_use = "iterators are lazy and do nothing unless consumed"]
+#[derive(Clone)]
+pub struct Components<'a> {
+    inner: std::str::Split<'a, char>,
+}
+
+impl<'a> Iterator for Components<'a> {
+    type Item = Component<'a>;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner
+            .next()
+            .map(RefStr::from_str)
+            .map(Cow::from)
+            .map(Component)
+    }
+}
+
+impl DoubleEndedIterator for Components<'_> {
+    #[inline]
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.inner
+            .next_back()
+            .map(RefStr::from_str)
+            .map(Cow::from)
+            .map(Component)
+    }
+}
+
+impl<'a> From<&'a RefStr> for Components<'a> {
+    #[inline]
+    fn from(rs: &'a RefStr) -> Self {
+        Self {
+            inner: rs.as_str().split('/'),
+        }
+    }
+}
+
+/// A path component of a [`RefStr`].
+///
+/// A [`Component`] is a valid [`RefStr`] which does not contain any '/'
+/// separators.
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Component<'a>(Cow<'a, RefStr>);
+
+impl<'a> Component<'a> {
+    #[inline]
+    pub fn from_refstr(r: impl Into<Cow<'a, RefStr>>) -> Option<Self> {
+        let r = r.into();
+        if !r.contains('/') {
+            Some(Self(r))
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    pub fn as_lit<T: lit::Lit>(&self) -> Option<T> {
+        T::from_component(self)
+    }
+
+    #[inline]
+    pub fn into_inner(self) -> Cow<'a, RefStr> {
+        self.0
+    }
+}
+
+impl Deref for Component<'_> {
+    type Target = RefStr;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<RefStr> for Component<'_> {
+    #[inline]
+    fn as_ref(&self) -> &RefStr {
+        self
+    }
+}
+
+impl<'a> From<&'a RefStr> for Option<Component<'a>> {
+    #[inline]
+    fn from(r: &'a RefStr) -> Self {
+        if !r.contains('/') {
+            Some(Component(Cow::from(r)))
+        } else {
+            None
+        }
+    }
+}
+
+impl<'a> From<Component<'a>> for Cow<'a, RefStr> {
+    #[inline]
+    fn from(c: Component<'a>) -> Self {
+        c.0
+    }
+}
+
+impl<T: lit::Lit> From<T> for Component<'static> {
+    #[inline]
+    fn from(_: T) -> Self {
+        Component(Cow::from(T::NAME))
+    }
+}
+
+impl<'a> From<lit::SomeLit<'a>> for Component<'a> {
+    #[inline]
+    fn from(s: lit::SomeLit<'a>) -> Self {
+        use lit::SomeLit::*;
+
+        match s {
+            Known(k) => k.into(),
+            Any(c) => c,
+        }
+    }
+}
+
+impl Display for Component<'_> {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(self.0.as_str())
+    }
+}
+
+pub mod component {
+    use super::Component;
+    use crate::name;
+    use std::borrow::Cow;
+
+    pub const HEADS: Component = Component(Cow::Borrowed(name::HEADS));
+    pub const MAIN: Component = Component(Cow::Borrowed(name::MAIN));
+    pub const MASTER: Component = Component(Cow::Borrowed(name::MASTER));
+    pub const NAMESPACES: Component = Component(Cow::Borrowed(name::NAMESPACES));
+    pub const NOTES: Component = Component(Cow::Borrowed(name::NOTES));
+    pub const ORIGIN: Component = Component(Cow::Borrowed(name::ORIGIN));
+    pub const REFS: Component = Component(Cow::Borrowed(name::REFS));
+    pub const REMOTES: Component = Component(Cow::Borrowed(name::REMOTES));
+    pub const TAGS: Component = Component(Cow::Borrowed(name::TAGS));
+}

crates/radicle-git-ref-format/src/refspec.rs

@@ -0,0 +1,605 @@
+use std::{
+    borrow::{Borrow, Cow},
+    convert::TryFrom,
+    fmt::{self, Display, Write as _},
+    iter::FromIterator,
+    ops::Deref,
+};
+
+use thiserror::Error;
+
+use crate::{check, lit, Namespaced, Qualified, RefStr, RefString};
+
+mod iter;
+pub use iter::{component, Component, Components, Iter};
+
+pub const STAR: &PatternStr = PatternStr::from_str("*");
+
+const CHECK_OPTS: check::Options = check::Options {
+    allow_onelevel: true,
+    allow_pattern: true,
+};
+
+#[repr(transparent)]
+#[derive(Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct PatternStr(str);
+
+impl PatternStr {
+    #[inline]
+    pub fn try_from_str(s: &str) -> Result<&Self, check::Error> {
+        TryFrom::try_from(s)
+    }
+
+    #[inline]
+    pub fn as_str(&self) -> &str {
+        self
+    }
+
+    pub fn join<R>(&self, other: R) -> PatternString
+    where
+        R: AsRef<RefStr>,
+    {
+        self._join(other.as_ref())
+    }
+
+    fn _join(&self, other: &RefStr) -> PatternString {
+        let mut buf = self.to_owned();
+        buf.push(other);
+        buf
+    }
+
+    #[inline]
+    pub fn qualified<'a>(&'a self) -> Option<QualifiedPattern<'a>> {
+        QualifiedPattern::from_patternstr(self)
+    }
+
+    #[inline]
+    pub fn to_namespaced<'a>(&'a self) -> Option<NamespacedPattern<'a>> {
+        self.into()
+    }
+
+    #[inline]
+    pub fn iter<'a>(&'a self) -> Iter<'a> {
+        self.0.split('/')
+    }
+
+    #[inline]
+    pub fn components<'a>(&'a self) -> Components<'a> {
+        Components::from(self)
+    }
+
+    pub(crate) const fn from_str(s: &str) -> &PatternStr {
+        unsafe { &*(s as *const str as *const PatternStr) }
+    }
+}
+
+impl Deref for PatternStr {
+    type Target = str;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<str> for PatternStr {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self
+    }
+}
+
+impl AsRef<Self> for PatternStr {
+    #[inline]
+    fn as_ref(&self) -> &Self {
+        self
+    }
+}
+
+impl<'a> TryFrom<&'a str> for &'a PatternStr {
+    type Error = check::Error;
+
+    #[inline]
+    fn try_from(s: &'a str) -> Result<Self, Self::Error> {
+        check::ref_format(CHECK_OPTS, s).map(|()| PatternStr::from_str(s))
+    }
+}
+
+impl<'a> From<&'a RefStr> for &'a PatternStr {
+    #[inline]
+    fn from(rs: &'a RefStr) -> Self {
+        PatternStr::from_str(rs.as_str())
+    }
+}
+
+impl<'a> From<&'a PatternStr> for Cow<'a, PatternStr> {
+    #[inline]
+    fn from(p: &'a PatternStr) -> Cow<'a, PatternStr> {
+        Cow::Borrowed(p)
+    }
+}
+
+impl Display for PatternStr {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(self)
+    }
+}
+
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct PatternString(pub(crate) String);
+
+impl PatternString {
+    #[inline]
+    pub fn as_str(&self) -> &str {
+        self.as_ref()
+    }
+
+    #[inline]
+    pub fn as_pattern_str(&self) -> &PatternStr {
+        self.as_ref()
+    }
+
+    #[inline]
+    pub fn from_components<'a, T>(iter: T) -> Result<Self, DuplicateGlob>
+    where
+        T: IntoIterator<Item = Component<'a>>,
+    {
+        iter.into_iter().collect()
+    }
+
+    #[inline]
+    pub fn and<R>(mut self, other: R) -> Self
+    where
+        R: AsRef<RefStr>,
+    {
+        self._push(other.as_ref());
+        self
+    }
+
+    #[inline]
+    pub fn push<R>(&mut self, other: R)
+    where
+        R: AsRef<RefStr>,
+    {
+        self._push(other.as_ref())
+    }
+
+    fn _push(&mut self, other: &RefStr) {
+        self.0.push('/');
+        self.0.push_str(other.as_str());
+    }
+
+    #[inline]
+    pub fn pop(&mut self) -> bool {
+        match self.0.rfind('/') {
+            None => false,
+            Some(idx) => {
+                self.0.truncate(idx);
+                true
+            }
+        }
+    }
+}
+
+impl Deref for PatternString {
+    type Target = PatternStr;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        self.borrow()
+    }
+}
+
+impl AsRef<PatternStr> for PatternString {
+    #[inline]
+    fn as_ref(&self) -> &PatternStr {
+        self
+    }
+}
+
+impl AsRef<str> for PatternString {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+impl Borrow<PatternStr> for PatternString {
+    #[inline]
+    fn borrow(&self) -> &PatternStr {
+        PatternStr::from_str(self.0.as_str())
+    }
+}
+
+impl ToOwned for PatternStr {
+    type Owned = PatternString;
+
+    #[inline]
+    fn to_owned(&self) -> Self::Owned {
+        PatternString(self.0.to_owned())
+    }
+}
+
+impl From<RefString> for PatternString {
+    #[inline]
+    fn from(rs: RefString) -> Self {
+        Self(rs.into())
+    }
+}
+
+impl<'a> From<&'a PatternString> for Cow<'a, PatternStr> {
+    #[inline]
+    fn from(p: &'a PatternString) -> Cow<'a, PatternStr> {
+        Cow::Borrowed(p.as_ref())
+    }
+}
+
+impl From<PatternString> for String {
+    #[inline]
+    fn from(p: PatternString) -> Self {
+        p.0
+    }
+}
+
+impl TryFrom<&str> for PatternString {
+    type Error = check::Error;
+
+    #[inline]
+    fn try_from(s: &str) -> Result<Self, Self::Error> {
+        PatternStr::try_from_str(s).map(ToOwned::to_owned)
+    }
+}
+
+impl TryFrom<String> for PatternString {
+    type Error = check::Error;
+
+    #[inline]
+    fn try_from(s: String) -> Result<Self, Self::Error> {
+        check::ref_format(CHECK_OPTS, s.as_str()).map(|()| PatternString(s))
+    }
+}
+
+#[derive(Debug, Error)]
+#[error("more than one '*' encountered")]
+pub struct DuplicateGlob;
+
+impl<'a> FromIterator<Component<'a>> for Result<PatternString, DuplicateGlob> {
+    fn from_iter<T>(iter: T) -> Self
+    where
+        T: IntoIterator<Item = Component<'a>>,
+    {
+        use Component::*;
+
+        let mut buf = String::new();
+        let mut seen_glob = false;
+        for c in iter {
+            if let Glob(_) = c {
+                if seen_glob {
+                    return Err(DuplicateGlob);
+                }
+
+                seen_glob = true;
+            }
+
+            buf.push_str(c.as_str());
+            buf.push('/');
+        }
+        buf.truncate(buf.len() - 1);
+
+        Ok(PatternString(buf))
+    }
+}
+
+impl Display for PatternString {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+/// A fully-qualified refspec.
+///
+/// A refspec is qualified _iff_ it starts with "refs/" and has at least three
+/// components. This implies that a [`QualifiedPattern`] ref has a category,
+/// such as "refs/heads/*".
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct QualifiedPattern<'a>(pub(crate) Cow<'a, PatternStr>);
+
+impl<'a> QualifiedPattern<'a> {
+    pub fn from_patternstr(r: impl Into<Cow<'a, PatternStr>>) -> Option<Self> {
+        Self::_from_patternstr(r.into())
+    }
+
+    fn _from_patternstr(r: Cow<'a, PatternStr>) -> Option<Self> {
+        let mut iter = r.iter();
+        match (iter.next()?, iter.next()?, iter.next()?) {
+            ("refs", _, _) => Some(QualifiedPattern(r)),
+            _ => None,
+        }
+    }
+
+    #[inline]
+    pub fn as_str(&self) -> &str {
+        self.as_ref()
+    }
+
+    #[inline]
+    pub fn join<'b, R>(&self, other: R) -> QualifiedPattern<'b>
+    where
+        R: AsRef<RefStr>,
+    {
+        QualifiedPattern(Cow::Owned(self.0.join(other)))
+    }
+
+    #[inline]
+    pub fn to_namespaced(&'a self) -> Option<NamespacedPattern<'a>> {
+        self.0.as_ref().into()
+    }
+
+    /// Add a namespace.
+    ///
+    /// Creates a new [`NamespacedPattern`] by prefxing `self` with
+    /// `refs/namespaces/<ns>`.
+    pub fn with_namespace<'b>(
+        &self,
+        ns: Component<'b>,
+    ) -> Result<NamespacedPattern<'a>, DuplicateGlob> {
+        PatternString::from_components(
+            IntoIterator::into_iter([lit::Refs.into(), lit::Namespaces.into(), ns])
+                .chain(self.components()),
+        )
+        .map(|pat| NamespacedPattern(Cow::Owned(pat)))
+    }
+
+    /// Like [`Self::non_empty_components`], but with string slices.
+    pub fn non_empty_iter(&'a self) -> (&'a str, &'a str, &'a str, Iter<'a>) {
+        let mut iter = self.iter();
+        (
+            iter.next().unwrap(),
+            iter.next().unwrap(),
+            iter.next().unwrap(),
+            iter,
+        )
+    }
+
+    /// Return the first three [`Component`]s, and a possibly empty iterator
+    /// over the remaining ones.
+    ///
+    /// A qualified ref is guaranteed to have at least three components, which
+    /// this method provides a witness of. This is useful eg. for pattern
+    /// matching on the prefix.
+    pub fn non_empty_components(
+        &'a self,
+    ) -> (Component<'a>, Component<'a>, Component<'a>, Components<'a>) {
+        let mut cs = self.components();
+        (
+            cs.next().unwrap(),
+            cs.next().unwrap(),
+            cs.next().unwrap(),
+            cs,
+        )
+    }
+
+    #[inline]
+    pub fn to_owned<'b>(&self) -> QualifiedPattern<'b> {
+        QualifiedPattern(Cow::Owned(self.0.clone().into_owned()))
+    }
+
+    #[inline]
+    pub fn into_owned<'b>(self) -> QualifiedPattern<'b> {
+        QualifiedPattern(Cow::Owned(self.0.into_owned()))
+    }
+
+    #[inline]
+    pub fn into_patternstring(self) -> PatternString {
+        self.into()
+    }
+}
+
+impl Deref for QualifiedPattern<'_> {
+    type Target = PatternStr;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<PatternStr> for QualifiedPattern<'_> {
+    #[inline]
+    fn as_ref(&self) -> &PatternStr {
+        self
+    }
+}
+
+impl AsRef<str> for QualifiedPattern<'_> {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+impl AsRef<Self> for QualifiedPattern<'_> {
+    #[inline]
+    fn as_ref(&self) -> &Self {
+        self
+    }
+}
+
+impl Display for QualifiedPattern<'_> {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<'a> From<Qualified<'a>> for QualifiedPattern<'a> {
+    #[inline]
+    fn from(q: Qualified<'a>) -> Self {
+        Self(Cow::Owned(q.into_refstring().into()))
+    }
+}
+
+impl<'a> From<QualifiedPattern<'a>> for Cow<'a, PatternStr> {
+    #[inline]
+    fn from(q: QualifiedPattern<'a>) -> Self {
+        q.0
+    }
+}
+
+impl From<QualifiedPattern<'_>> for PatternString {
+    #[inline]
+    fn from(q: QualifiedPattern) -> Self {
+        q.0.into_owned()
+    }
+}
+
+/// A [`PatternString`] ref under a git namespace.
+///
+/// A ref is namespaced if it starts with "refs/namespaces/", another path
+/// component, and "refs/". Eg.
+///
+///     refs/namespaces/xyz/refs/heads/main
+///
+/// Note that namespaces can be nested, so the result of
+/// [`NamespacedPattern::strip_namespace`] may be convertible to a
+/// [`NamespacedPattern`] again. For example:
+///
+/// ```no_run
+/// let full = pattern!("refs/namespaces/a/refs/namespaces/b/refs/heads/*");
+/// let namespaced = full.to_namespaced().unwrap();
+/// let strip_first = namespaced.strip_namespace();
+/// let nested = strip_first.namespaced().unwrap();
+/// let strip_second = nested.strip_namespace();
+///
+/// assert_eq!("a", namespaced.namespace().as_str());
+/// assert_eq!("b", nested.namespace().as_str());
+/// assert_eq!("refs/namespaces/b/refs/heads/*", strip_first.as_str());
+/// assert_eq!("refs/heads/*", strip_second.as_str());
+/// ```
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct NamespacedPattern<'a>(Cow<'a, PatternStr>);
+
+impl<'a> NamespacedPattern<'a> {
+    pub fn namespace(&'a self) -> Component<'a> {
+        self.components().nth(2).unwrap()
+    }
+
+    pub fn strip_namespace(&self) -> PatternString {
+        PatternString::from_components(self.components().skip(3))
+            .expect("BUG: NamespacedPattern was constructed with a duplicate glob")
+    }
+
+    pub fn strip_namespace_recursive(&self) -> PatternString {
+        let mut strip = self.strip_namespace();
+        while let Some(ns) = strip.to_namespaced() {
+            strip = ns.strip_namespace();
+        }
+        strip
+    }
+
+    #[inline]
+    pub fn to_owned<'b>(&self) -> NamespacedPattern<'b> {
+        NamespacedPattern(Cow::Owned(self.0.clone().into_owned()))
+    }
+
+    #[inline]
+    pub fn into_owned<'b>(self) -> NamespacedPattern<'b> {
+        NamespacedPattern(Cow::Owned(self.0.into_owned()))
+    }
+
+    #[inline]
+    pub fn into_qualified(self) -> QualifiedPattern<'a> {
+        self.into()
+    }
+}
+
+impl Deref for NamespacedPattern<'_> {
+    type Target = PatternStr;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        self.borrow()
+    }
+}
+
+impl AsRef<PatternStr> for NamespacedPattern<'_> {
+    #[inline]
+    fn as_ref(&self) -> &PatternStr {
+        self.0.as_ref()
+    }
+}
+
+impl AsRef<str> for NamespacedPattern<'_> {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+impl Borrow<PatternStr> for NamespacedPattern<'_> {
+    #[inline]
+    fn borrow(&self) -> &PatternStr {
+        PatternStr::from_str(self.0.as_str())
+    }
+}
+
+impl<'a> From<Namespaced<'a>> for NamespacedPattern<'a> {
+    #[inline]
+    fn from(ns: Namespaced<'a>) -> Self {
+        NamespacedPattern(Cow::Owned(ns.to_ref_string().into()))
+    }
+}
+
+impl<'a> From<NamespacedPattern<'a>> for QualifiedPattern<'a> {
+    #[inline]
+    fn from(ns: NamespacedPattern<'a>) -> Self {
+        Self(ns.0)
+    }
+}
+
+impl<'a> From<&'a PatternStr> for Option<NamespacedPattern<'a>> {
+    fn from(rs: &'a PatternStr) -> Self {
+        let mut cs = rs.iter();
+        match (cs.next()?, cs.next()?, cs.next()?, cs.next()?) {
+            ("refs", "namespaces", _, "refs") => Some(NamespacedPattern(Cow::from(rs))),
+
+            _ => None,
+        }
+    }
+}
+
+impl Display for NamespacedPattern<'_> {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+/// A Git [refspec].
+///
+/// **Note** that this is a simplified version of a [refspec] where
+/// the `src` and `dst` are required and there is no way to construct
+/// a negative refspec, e.g. `^refs/heads/no-thanks`.
+///
+/// [refspec]: https://git-scm.com/book/en/v2/Git-Internals-The-Refspec
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Refspec<T, U> {
+    pub src: T,
+    pub dst: U,
+    pub force: bool,
+}
+
+impl<T, U> fmt::Display for Refspec<T, U>
+where
+    T: fmt::Display,
+    U: fmt::Display,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.force {
+            f.write_char('+')?;
+        }
+        write!(f, "{}:{}", self.src, self.dst)
+    }
+}

crates/radicle-git-ref-format/src/refspec/iter.rs

@@ -0,0 +1,98 @@
+use std::fmt::{self, Display};
+
+use super::PatternStr;
+use crate::{lit, RefStr};
+
+pub type Iter<'a> = std::str::Split<'a, char>;
+
+pub enum Component<'a> {
+    Glob(Option<&'a PatternStr>),
+    Normal(&'a RefStr),
+}
+
+impl Component<'_> {
+    #[inline]
+    pub fn as_str(&self) -> &str {
+        self.as_ref()
+    }
+}
+
+impl AsRef<str> for Component<'_> {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        match self {
+            Self::Glob(None) => "*",
+            Self::Glob(Some(x)) => x.as_str(),
+            Self::Normal(x) => x.as_str(),
+        }
+    }
+}
+
+impl Display for Component<'_> {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+impl<T: lit::Lit> From<T> for Component<'static> {
+    #[inline]
+    fn from(_: T) -> Self {
+        Self::Normal(T::NAME)
+    }
+}
+
+#[must_use = "iterators are lazy and do nothing unless consumed"]
+#[derive(Clone)]
+pub struct Components<'a> {
+    inner: Iter<'a>,
+}
+
+impl<'a> Iterator for Components<'a> {
+    type Item = Component<'a>;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next().map(|next| match next {
+            "*" => Component::Glob(None),
+            x if x.contains('*') => Component::Glob(Some(PatternStr::from_str(x))),
+            x => Component::Normal(RefStr::from_str(x)),
+        })
+    }
+}
+
+impl DoubleEndedIterator for Components<'_> {
+    #[inline]
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.inner.next_back().map(|next| match next {
+            "*" => Component::Glob(None),
+            x if x.contains('*') => Component::Glob(Some(PatternStr::from_str(x))),
+            x => Component::Normal(RefStr::from_str(x)),
+        })
+    }
+}
+
+impl<'a> From<&'a PatternStr> for Components<'a> {
+    #[inline]
+    fn from(p: &'a PatternStr) -> Self {
+        Self {
+            inner: p.as_str().split('/'),
+        }
+    }
+}
+
+pub mod component {
+    use super::Component;
+    use crate::name;
+
+    pub const STAR: Component = Component::Glob(None);
+    pub const HEADS: Component = Component::Normal(name::HEADS);
+    pub const MAIN: Component = Component::Normal(name::MAIN);
+    pub const MASTER: Component = Component::Normal(name::MASTER);
+    pub const NAMESPACES: Component = Component::Normal(name::NAMESPACES);
+    pub const NOTES: Component = Component::Normal(name::NOTES);
+    pub const ORIGIN: Component = Component::Normal(name::ORIGIN);
+    pub const REFS: Component = Component::Normal(name::REFS);
+    pub const REMOTES: Component = Component::Normal(name::REMOTES);
+    pub const TAGS: Component = Component::Normal(name::TAGS);
+}

crates/radicle-git-ref-format/src/serde.rs

@@ -0,0 +1,190 @@
+use std::convert::TryFrom;
+
+use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
+
+use crate::{
+    refspec::{NamespacedPattern, PatternStr, PatternString, QualifiedPattern},
+    Namespaced, Qualified, RefStr, RefString,
+};
+
+impl<'de: 'a, 'a> Deserialize<'de> for &'a RefStr {
+    #[inline]
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer)
+            .and_then(|s: &str| Self::try_from(s).map_err(de::Error::custom))
+    }
+}
+
+impl Serialize for &RefStr {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}
+
+impl<'de> Deserialize<'de> for RefString {
+    #[inline]
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer)
+            .and_then(|x: String| Self::try_from(x).map_err(de::Error::custom))
+    }
+}
+
+impl Serialize for RefString {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}
+
+impl<'de: 'a, 'a> Deserialize<'de> for &'a PatternStr {
+    #[inline]
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer)
+            .and_then(|s: &str| Self::try_from(s).map_err(de::Error::custom))
+    }
+}
+
+impl Serialize for &PatternStr {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}
+
+impl<'de> Deserialize<'de> for PatternString {
+    #[inline]
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer)
+            .and_then(|x: String| Self::try_from(x).map_err(de::Error::custom))
+    }
+}
+
+impl Serialize for PatternString {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}
+
+impl<'de> Deserialize<'de> for Qualified<'static> {
+    #[inline]
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer).and_then(|s: String| {
+            let s = RefString::try_from(s).map_err(de::Error::custom)?;
+            s.qualified()
+                .ok_or_else(|| de::Error::custom("not a qualified ref"))
+                .map(|q| q.into_owned())
+        })
+    }
+}
+
+impl Serialize for Qualified<'_> {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}
+
+impl<'de> Deserialize<'de> for Namespaced<'static> {
+    #[inline]
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer).and_then(|s: String| {
+            let s = RefString::try_from(s).map_err(de::Error::custom)?;
+            s.to_namespaced()
+                .ok_or_else(|| de::Error::custom("not a namespaced ref"))
+                .map(|ns| ns.into_owned())
+        })
+    }
+}
+
+impl Serialize for Namespaced<'_> {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}
+
+impl<'de> Deserialize<'de> for QualifiedPattern<'_> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer).and_then(|s: String| {
+            let s = PatternString::try_from(s).map_err(de::Error::custom)?;
+            s.qualified()
+                .ok_or_else(|| de::Error::custom("not a qualified ref"))
+                .map(|q| q.into_owned())
+        })
+    }
+}
+
+impl Serialize for QualifiedPattern<'_> {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}
+
+impl<'de> Deserialize<'de> for NamespacedPattern<'_> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer).and_then(|s: String| {
+            let s = PatternString::try_from(s).map_err(de::Error::custom)?;
+            s.to_namespaced()
+                .ok_or_else(|| de::Error::custom("not a qualified ref"))
+                .map(|q| q.into_owned())
+        })
+    }
+}
+
+impl Serialize for NamespacedPattern<'_> {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_str())
+    }
+}