feat: add Repository::head_tree_id_or_empty() for convenience.

Author: Byron

gix/src/repository/reference.rs

@@ -227,6 +227,22 @@ impl crate::Repository {
         Ok(self.head_commit()?.tree_id()?)
     }
 
+    /// Like [`Self::head_tree_id()`], but will return an empty tree hash if the repository HEAD is unborn.
+    pub fn head_tree_id_or_empty(&self) -> Result<crate::Id<'_>, reference::head_tree_id::Error> {
+        self.head_tree_id().or_else(|err| {
+            if let reference::head_tree_id::Error::HeadCommit(reference::head_commit::Error::PeelToCommit(
+                crate::head::peel::to_commit::Error::PeelToObject(crate::head::peel::to_object::Error::Unborn {
+                    ..
+                }),
+            )) = err
+            {
+                Ok(self.empty_tree().id())
+            } else {
+                Err(err)
+            }
+        })
+    }
+
     /// Return the tree object the `HEAD^{tree}` reference currently points to after peeling it fully,
     /// following symbolic references and tags until a tree is found.
     ///

gix/src/status/iter/mod.rs

@@ -45,17 +45,7 @@ where
 
         let obtain_tree_id = || -> Result<Option<gix_hash::ObjectId>, crate::status::into_iter::Error> {
             Ok(match self.head_tree {
-                Some(None) => match self.repo.head_tree_id() {
-                    Ok(id) => Some(id.into()),
-                    Err(crate::reference::head_tree_id::Error::HeadCommit(
-                        crate::reference::head_commit::Error::PeelToCommit(
-                            crate::head::peel::to_commit::Error::PeelToObject(
-                                crate::head::peel::to_object::Error::Unborn { .. },
-                            ),
-                        ),
-                    )) => Some(gix_hash::ObjectId::empty_tree(self.repo.object_hash())),
-                    Err(err) => return Err(err.into()),
-                },
+                Some(None) => Some(self.repo.head_tree_id_or_empty()?.into()),
                 Some(Some(tree_id)) => Some(tree_id),
                 None => None,
             })

gix/tests/gix/clone.rs

@@ -667,6 +667,7 @@ mod blocking_io {
             assert!(!repo.index_path().is_file(), "newly initialized repos have no index");
             let head = repo.head()?;
             assert!(head.is_unborn());
+            assert_eq!(repo.head_tree_id_or_empty()?, repo.empty_tree().id());
 
             assert!(
                 head.log_iter().all()?.is_none(),

gix/tests/gix/head.rs

@@ -12,6 +12,7 @@ mod peel {
             let commit = repo.head_commit()?;
             assert_eq!(commit.id, expected_commit);
             assert_eq!(repo.head_tree_id()?, commit.tree_id()?);
+            assert_eq!(repo.head_tree_id_or_empty()?, commit.tree_id()?);
             assert_eq!(repo.head()?.try_into_peeled_id()?.expect("born"), expected_commit);
             assert_eq!(repo.head()?.peel_to_object_in_place()?.id, expected_commit);
             assert_eq!(repo.head()?.try_peel_to_id_in_place()?.expect("born"), expected_commit);