feat!: optionally store objects new objects in memory only.

The default object database changed to a version that allows to
keep objects in memory. This needs a mutable `Repository` instance
to setup.

Author: Byron

gix/src/lib.rs

@@ -158,7 +158,10 @@ pub mod path;
 /// The standard type for a store to handle git references.
 pub type RefStore = gix_ref::file::Store;
 /// A handle for finding objects in an object database, abstracting away caches for thread-local use.
-pub type OdbHandle = gix_odb::Handle;
+pub type OdbHandle = gix_odb::memory::Proxy<gix_odb::Handle>;
+/// A handle for finding objects in an object database, abstracting away caches for moving across threads.
+pub type OdbHandleArc = gix_odb::memory::Proxy<gix_odb::HandleArc>;
+
 /// A way to access git configuration
 pub(crate) type Config = OwnShared<gix_config::File<'static>>;
 

gix/src/repository/cache.rs

@@ -39,3 +39,14 @@ impl crate::Repository {
         (ten_mb_for_every_10k_files as usize).max(4 * 1024)
     }
 }
+
+/// Handling of InMemory object writing
+impl crate::Repository {
+    /// When writing objects, keep them in memory instead of writing them to disk.
+    /// This makes any change to the object database non-persisting, while keeping the view
+    /// to the object database consistent for this instance.
+    pub fn with_object_memory(mut self) -> Self {
+        self.objects.enable_object_memory();
+        self
+    }
+}

gix/src/repository/impls.rs

@@ -38,7 +38,7 @@ impl From<&crate::ThreadSafeRepository> for crate::Repository {
     fn from(repo: &crate::ThreadSafeRepository) -> Self {
         crate::Repository::from_refs_and_objects(
             repo.refs.clone(),
-            repo.objects.to_handle().into(),
+            gix_odb::memory::Proxy::from(gix_odb::Cache::from(repo.objects.to_handle())).with_write_passthrough(),
             repo.work_tree.clone(),
             repo.common_dir.clone(),
             repo.config.clone(),
@@ -56,7 +56,7 @@ impl From<crate::ThreadSafeRepository> for crate::Repository {
     fn from(repo: crate::ThreadSafeRepository) -> Self {
         crate::Repository::from_refs_and_objects(
             repo.refs,
-            repo.objects.to_handle().into(),
+            gix_odb::memory::Proxy::from(gix_odb::Cache::from(repo.objects.to_handle())).with_write_passthrough(),
             repo.work_tree,
             repo.common_dir,
             repo.config,

gix/src/repository/object.rs

@@ -109,7 +109,7 @@ impl crate::Repository {
     #[doc(alias = "exists", alias = "git2")]
     pub fn has_object(&self, id: impl AsRef<gix_hash::oid>) -> bool {
         let id = id.as_ref();
-        if id == ObjectId::empty_tree(self.object_hash()) {
+        if id.to_owned().is_empty_tree() {
             true
         } else {
             self.objects.exists(id)

gix/src/types.rs

@@ -247,7 +247,7 @@ pub struct PathspecDetached {
     /// The prepared search to use for checking matches.
     pub search: gix_pathspec::Search,
     /// A thread-safe version of an ODB.
-    pub odb: gix_odb::HandleArc,
+    pub odb: crate::OdbHandleArc,
 }
 
 /// A stand-in for the submodule of a particular name.

gix/tests/repository/object.rs

@@ -229,8 +229,24 @@ mod write_blob {
     #[test]
     fn from_slice() -> crate::Result {
         let (_tmp, repo) = empty_bare_repo()?;
+        let expected = hex_to_id("95d09f2b10159347eece71399a7e2e907ea3df4f");
+        assert!(!repo.has_object(expected));
+
         let oid = repo.write_blob(b"hello world")?;
-        assert_eq!(oid, hex_to_id("95d09f2b10159347eece71399a7e2e907ea3df4f"));
+        assert_eq!(oid, expected);
+
+        let mut other_repo = gix::open_opts(repo.path(), gix::open::Options::isolated())?;
+        other_repo.objects.enable_object_memory();
+        assert!(
+            other_repo.has_object(oid),
+            "we definitely don't accidentally write to memory only"
+        );
+        let in_memory_id = other_repo.write_blob("hello world - to memory")?;
+        assert!(!repo.has_object(in_memory_id), "the object was never written to disk…");
+        assert!(
+            other_repo.has_object(in_memory_id),
+            "…and exists only in the instance that wrote it"
+        );
         Ok(())
     }