feat: FullNameRef::file_name() (#298)

git-ref/src/fullname.rs

@@ -106,4 +106,10 @@ impl<'a> FullNameRef<'a> {
     pub fn to_owned(&self) -> FullName {
         FullName(self.0.to_owned())
     }
+
+    /// Return the file name portion of a full name, for instance `main` if the
+    /// full name was `refs/heads/main`.
+    pub fn file_name(&self) -> &BStr {
+        self.0.rsplitn(2, |b| *b == b'/').next().expect("valid ref").as_bstr()
+    }
 }

git-ref/src/name.rs

@@ -13,6 +13,8 @@ pub type Error = git_validate::reference::name::Error;
 
 impl<'a> FullNameRef<'a> {
     /// Convert this name into the relative path identifying the reference location.
+    // TODO: use custom `Path` type instead, as this isn't really a path. See ref iteration with prefix for
+    //       similar comment.
     pub fn to_path(self) -> Cow<'a, Path> {
         self.0.to_path().expect("UTF-8 conversion always succeeds").into()
     }

git-ref/tests/fullname/mod.rs

@@ -1,5 +1,11 @@
 use std::convert::TryInto;
 
+#[test]
+fn file_name() {
+    let name: git_ref::FullName = "refs/heads/main".try_into().unwrap();
+    assert_eq!(name.to_ref().file_name(), "main");
+}
+
 #[test]
 fn prefix_with_namespace_and_stripping() {
     let ns = git_ref::namespace::expand("foo").unwrap();