feat!: diff::resource_cache() now takes the attribute stack directly.

That way, the constructor becaomes more versatile as the user can chose
to pass attribute stacks that have more functionality, and thus can be
used in more places.

Author: Byron

gix/src/diff.rs

@@ -56,8 +56,6 @@ mod utils {
             DiffPipelineOptions(#[from] crate::config::diff::pipeline_options::Error),
             #[error(transparent)]
             CommandContext(#[from] crate::config::command_context::Error),
-            #[error(transparent)]
-            AttributeStack(#[from] crate::config::attribute_stack::Error),
         }
     }
 
@@ -102,18 +100,16 @@ mod utils {
     /// Return a low-level utility to efficiently prepare a the blob-level diff operation between two resources,
     /// and cache these diffable versions so that matrix-like MxN diffs are efficient.
     ///
-    /// `repo` is used to obtain the needed configuration values, and `index` is used to potentially read `.gitattributes`
-    /// files from which may affect the diff operation.
+    /// `repo` is used to obtain the needed configuration values.
     /// `mode` determines how the diffable files will look like, and also how fast, in average, these conversions are.
-    /// `attribute_source` controls where `.gitattributes` will be read from, and it's typically adjusted based on the
+    /// `attr_stack` is for accessing `.gitattributes` for knowing how to apply filters. Noow that it's typically adjusted based on the
     /// `roots` - if there are no worktree roots, `.gitattributes` are also not usually read from worktrees.
     /// `roots` provide information about where to get diffable data from, so source and destination can either be sourced from
     /// a worktree, or from the object database, or both.
     pub fn resource_cache(
         repo: &Repository,
-        index: &gix_index::State,
         mode: gix_diff::blob::pipeline::Mode,
-        attribute_source: gix_worktree::stack::state::attributes::Source,
+        attr_stack: gix_worktree::Stack,
         roots: gix_diff::blob::pipeline::WorktreeRoots,
     ) -> Result<gix_diff::blob::Platform, resource_cache::Error> {
         let diff_algo = repo.config.diff_algorithm()?;
@@ -129,13 +125,7 @@ mod utils {
                 repo.config.diff_pipeline_options()?,
             ),
             mode,
-            repo.attributes_only(
-                // TODO(perf): this could benefit from not having to build an intermediate index,
-                //             and traverse the a tree directly.
-                index,
-                attribute_source,
-            )?
-            .inner,
+            attr_stack,
         );
         Ok(diff_cache)
     }

gix/src/repository/diff.rs

@@ -10,6 +10,8 @@ pub mod resource_cache {
         ResourceCache(#[from] crate::diff::resource_cache::Error),
         #[error(transparent)]
         Index(#[from] crate::repository::index_or_load_from_head::Error),
+        #[error(transparent)]
+        AttributeStack(#[from] crate::config::attribute_stack::Error),
     }
 }
 
@@ -30,15 +32,19 @@ impl Repository {
         mode: gix_diff::blob::pipeline::Mode,
         worktree_roots: gix_diff::blob::pipeline::WorktreeRoots,
     ) -> Result<gix_diff::blob::Platform, resource_cache::Error> {
+        let index = self.index_or_load_from_head()?;
         Ok(crate::diff::resource_cache(
             self,
-            &*self.index_or_load_from_head()?,
             mode,
-            if worktree_roots.new_root.is_some() || worktree_roots.old_root.is_some() {
-                gix_worktree::stack::state::attributes::Source::WorktreeThenIdMapping
-            } else {
-                gix_worktree::stack::state::attributes::Source::IdMapping
-            },
+            self.attributes_only(
+                &index,
+                if worktree_roots.new_root.is_some() || worktree_roots.old_root.is_some() {
+                    gix_worktree::stack::state::attributes::Source::WorktreeThenIdMapping
+                } else {
+                    gix_worktree::stack::state::attributes::Source::IdMapping
+                },
+            )?
+            .inner,
             worktree_roots,
         )?)
     }

gix/tests/diff/mod.rs

@@ -5,11 +5,12 @@ use crate::util::named_repo;
 #[test]
 fn resource_cache() -> crate::Result {
     let repo = named_repo("make_diff_repo.sh")?;
+    let index = repo.index()?;
     let cache = gix::diff::resource_cache(
         &repo,
-        &*repo.index()?,
         gix::diff::blob::pipeline::Mode::ToWorktreeAndBinaryToText,
-        gix_worktree::stack::state::attributes::Source::IdMapping,
+        repo.attributes_only(&index, gix_worktree::stack::state::attributes::Source::IdMapping)?
+            .detach(),
         Default::default(),
     )?;
     assert_eq!(