fix: prevent panic in Repository::rev_parse_single() when HEAD was invalid.

When using a refspec like `HEAD:file`.

Author: Byron

gix/src/revision/spec/parse/delegate/mod.rs

@@ -203,11 +203,16 @@ impl<'repo> Delegate<'repo> {
         for (r, obj) in self.refs.iter().zip(self.objs.iter_mut()) {
             if let (Some(ref_), obj_opt @ None) = (r, obj) {
                 if let Some(id) = ref_.target.try_id().map(ToOwned::to_owned).or_else(|| {
-                    ref_.clone()
-                        .attach(repo)
-                        .peel_to_id_in_place()
-                        .ok()
-                        .map(crate::Id::detach)
+                    match ref_.clone().attach(repo).peel_to_id_in_place() {
+                        Err(err) => {
+                            self.err.push(Error::PeelToId {
+                                name: ref_.name.clone(),
+                                source: err,
+                            });
+                            None
+                        }
+                        Ok(id) => Some(id.detach()),
+                    }
                 }) {
                     obj_opt.get_or_insert_with(HashSet::default).insert(id);
                 };

gix/src/revision/spec/parse/types.rs

@@ -55,6 +55,11 @@ pub struct Options {
 #[derive(Debug, thiserror::Error)]
 #[allow(missing_docs)]
 pub enum Error {
+    #[error("Could not peel '{}' to obtain its target", name)]
+    PeelToId {
+        name: gix_ref::FullName,
+        source: reference::peel::Error,
+    },
     #[error("The rev-spec is malformed and misses a ref name")]
     Malformed,
     #[error("Unborn heads do not have a reflog yet")]

gix/tests/revision/spec/from_bytes/mod.rs

@@ -147,11 +147,11 @@ fn access_blob_through_tree() {
 #[test]
 fn invalid_head() {
     let repo = repo("invalid-head").unwrap();
+    let err = parse_spec("HEAD:file", &repo).unwrap_err();
+    assert_eq!(err.to_string(), "Could not peel 'HEAD' to obtain its target");
+
     let err = parse_spec("HEAD", &repo).unwrap_err();
     assert_eq!(err.to_string(), "The rev-spec is malformed and misses a ref name");
-
-    let err = parse_spec("HEAD:file", &repo).unwrap_err();
-    assert_eq!(err.to_string(), "TBD");
 }
 
 #[test]