fix match_group::Item to make it uniform with how we typically name refs (#450)

Author: Byron

git-refspec/src/match_group/mod.rs

@@ -88,7 +88,7 @@ impl<'a> MatchGroup<'a> {
                             .matches_lhs(Item {
                                 full_ref_name: name,
                                 target: &null_id,
-                                tag: None,
+                                object: None,
                             })
                             .0
                     }

git-refspec/src/match_group/types.rs

@@ -25,10 +25,10 @@ pub struct Outcome<'spec, 'item> {
 pub struct Item<'a> {
     /// The full name of the references, like `refs/heads/main`
     pub full_ref_name: &'a BStr,
-    /// The peeled id it points to that we should match against.
+    /// The id that `full_ref_name` points to, which typically is a commit, but can also be a tag object (or anything else).
     pub target: &'a oid,
-    /// The tag object's id if this is a tag
-    pub tag: Option<&'a oid>,
+    /// The object an annotated tag is pointing to, if `target` is an annotated tag.
+    pub object: Option<&'a oid>,
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]

git-refspec/src/match_group/util.rs

@@ -111,8 +111,8 @@ impl<'a> Needle<'a> {
                 if *id == item.target {
                     return Match::Normal;
                 }
-                match item.tag {
-                    Some(tag) if tag == *id => Match::Normal,
+                match item.object {
+                    Some(object) if object == *id => Match::Normal,
                     _ => Match::None,
                 }
             }

git-refspec/tests/matching/mod.rs

@@ -18,16 +18,16 @@ pub mod baseline {
     pub struct Ref {
         pub name: BString,
         pub target: ObjectId,
-        /// Set if this is a tag, pointing to the tag object itself
-        pub tag: Option<ObjectId>,
+        /// Set if `target` is an annotated tag, this being the object it points to.
+        pub object: Option<ObjectId>,
     }
 
     impl Ref {
         pub fn to_item(&self) -> git_refspec::match_group::Item<'_> {
             git_refspec::match_group::Item {
                 full_ref_name: self.name.borrow(),
                 target: &self.target,
-                tag: self.tag.as_deref(),
+                object: self.object.as_deref(),
             }
         }
     }
@@ -216,13 +216,10 @@ pub mod baseline {
                 out.push(Ref {
                     name: name.into(),
                     target,
-                    tag: None,
+                    object: None,
                 })
             } else {
-                let last = out.last_mut().unwrap();
-                let tag = last.target;
-                last.target = target;
-                last.tag = Some(tag);
+                out.last_mut().unwrap().object = Some(target);
             }
         }
         Ok(out)