fix: LineRef is now Copy and remove non-exhaustive

After all, this struct refers to what's in a reflog line, which is stable.

Author: Byron

gix-ref/src/store/file/log/line.rs

@@ -5,7 +5,7 @@ use crate::{log::Line, store_impl::file::log::LineRef};
 impl<'a> LineRef<'a> {
     /// Convert this instance into its mutable counterpart
     pub fn to_owned(&self) -> Line {
-        self.clone().into()
+        (*self).into()
     }
 }
 

gix-ref/src/store/file/log/mod.rs

@@ -8,9 +8,8 @@ pub mod iter;
 mod line;
 
 /// A parsed ref log line.
-#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
+#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
-#[non_exhaustive]
 pub struct LineRef<'a> {
     /// The previous object id in hexadecimal. Use [`LineRef::previous_oid()`] to get a more usable form.
     pub previous_oid: &'a BStr,