Add method to get owned commit of branch

src/repo.rs

@@ -1435,7 +1435,7 @@ impl<'a> Branch<'a> {
     }
 }
 
-impl Branch<'_> {
+impl<'a> Branch<'a> {
     pub fn commit(&self) -> Result<Commit, String> {
         Ok(Commit(
             self.0
@@ -1445,6 +1445,15 @@ impl Branch<'_> {
         ))
     }
 
+    pub fn commit_owned(self) -> Result<Commit<'a>, String> {
+        Ok(Commit(
+            self.0
+                .into_reference()
+                .peel_to_commit()
+                .map_err(convert_libgit2_error)?,
+        ))
+    }
+
     pub fn set_upstream(&mut self, remote_name: &str, branch_name: &str) -> Result<(), String> {
         self.0
             .set_upstream(Some(&format!("{}/{}", remote_name, branch_name)))