various improvements

gix/src/repository/impls.rs

@@ -1,3 +1,4 @@
+use gix_hash::ObjectId;
 use gix_object::Exists;
 use std::ops::DerefMut;
 
@@ -129,6 +130,12 @@ impl gix_object::Write for crate::Repository {
 
 impl gix_object::FindHeader for crate::Repository {
     fn try_header(&self, id: &gix_hash::oid) -> Result<Option<gix_object::Header>, gix_object::find::Error> {
+        if id == ObjectId::empty_tree(self.object_hash()) {
+            return Ok(Some(gix_object::Header {
+                kind: gix_object::Kind::Tree,
+                size: 0,
+            }));
+        }
         self.objects.try_header(id)
     }
 }
@@ -139,12 +146,22 @@ impl gix_object::Find for crate::Repository {
         id: &gix_hash::oid,
         buffer: &'a mut Vec<u8>,
     ) -> Result<Option<gix_object::Data<'a>>, gix_object::find::Error> {
+        if id == ObjectId::empty_tree(self.object_hash()) {
+            buffer.clear();
+            return Ok(Some(gix_object::Data {
+                kind: gix_object::Kind::Tree,
+                data: &[],
+            }));
+        }
         self.objects.try_find(id, buffer)
     }
 }
 
 impl gix_object::Exists for crate::Repository {
     fn exists(&self, id: &gix_hash::oid) -> bool {
+        if id == ObjectId::empty_tree(self.object_hash()) {
+            return true;
+        }
         self.objects.exists(id)
     }
 }

gix/src/repository/index.rs

@@ -140,7 +140,7 @@ impl crate::Repository {
     /// Note that this is an expensive operation as it requires recursively traversing the entire tree to unpack it into the index.
     pub fn index_from_tree(&self, tree: &gix_hash::oid) -> Result<gix_index::File, super::index_from_tree::Error> {
         Ok(gix_index::File::from_state(
-            gix_index::State::from_tree(tree, &self.objects, self.config.protect_options()?).map_err(|err| {
+            gix_index::State::from_tree(tree, self, self.config.protect_options()?).map_err(|err| {
                 super::index_from_tree::Error::IndexFromTree {
                     id: tree.into(),
                     source: err,

gix/src/status/iter/mod.rs

@@ -53,7 +53,7 @@ where
                                 crate::head::peel::to_object::Error::Unborn { .. },
                             ),
                         ),
-                    )) => None,
+                    )) => Some(gix_hash::ObjectId::empty_tree(self.repo.object_hash())),
                     Err(err) => return Err(err.into()),
                 },
                 Some(Some(tree_id)) => Some(tree_id),

gix/tests/fixtures/make_status_repos.sh

@@ -34,4 +34,10 @@ git init racy-git
 git init untracked-unborn
 (cd untracked-unborn
   touch untracked
-)
+)
+
+git init untracked-added
+(cd untracked-added
+  echo content >added
+  git add added
+)

gix/tests/gix/repository/object.rs

@@ -1,6 +1,32 @@
 use crate::util::named_subrepo_opts;
 use gix_testtools::tempfile;
 
+mod object_database_impl {
+    use gix_object::{Exists, Find, FindHeader};
+
+    #[test]
+    fn empty_tree_is_always_present() -> crate::Result {
+        let repo = crate::named_subrepo_opts("make_basic_repo.sh", "unborn", gix::open::Options::isolated())?;
+        let empty_tree = gix::ObjectId::empty_tree(repo.object_hash());
+        assert!(repo.exists(&empty_tree));
+        assert_eq!(
+            repo.try_header(&empty_tree)?.expect("tree present"),
+            gix_object::Header {
+                kind: gix_object::Kind::Tree,
+                size: 0
+            }
+        );
+        let mut buf = repo.empty_reusable_buffer();
+        buf.push(42);
+        assert_eq!(
+            repo.try_find(&empty_tree, &mut buf)?.expect("tree present").kind,
+            gix_object::Kind::Tree
+        );
+        assert_eq!(buf.len(), 0, "the data in the buffer matches the empty tree");
+        Ok(())
+    }
+}
+
 #[cfg(feature = "tree-editor")]
 mod edit_tree {
     use crate::util::hex_to_id;

gix/tests/gix/status.rs

@@ -113,6 +113,29 @@ mod into_iter {
         Ok(())
     }
 
+    #[test]
+    fn untracked_added() -> crate::Result {
+        let repo = repo("untracked-added")?;
+        let mut status = repo.status(gix::progress::Discard)?.into_iter(None)?;
+        let mut items: Vec<_> = status.by_ref().filter_map(Result::ok).collect();
+        items.sort_by(|a, b| a.location().cmp(b.location()));
+        insta::assert_debug_snapshot!(items, @r#"
+        [
+            TreeIndex(
+                Addition {
+                    location: "added",
+                    index: 0,
+                    entry_mode: Mode(
+                        FILE,
+                    ),
+                    id: Sha1(d95f3ad14dee633a758d2e331151e950dd13e4ed),
+                },
+            ),
+        ]
+        "#);
+        Ok(())
+    }
+
     #[test]
     fn error_during_tree_traversal_causes_failure() -> crate::Result {
         let repo = repo("untracked-only")?;