refactor: remove unnecessary unsafe by using chunks_mut()

This was probably a left-over from times where there was a static
requirement on the chunks processing. Maybe… .

Author: Byron

README.md

@@ -90,10 +90,10 @@ Follow linked crate name for detailed status. Please note that all crates follow
   * `gitoxide-core`
 * **very early**    
   * [git-index](https://github.com/Byron/gitoxide/blob/main/crate-status.md#git-index)
+  * [git-worktree](https://github.com/Byron/gitoxide/blob/main/crate-status.md#git-worktree)
   * [git-bitmap](https://github.com/Byron/gitoxide/blob/main/crate-status.md#git-bitmap)
 * **idea**
   * [git-revision](https://github.com/Byron/gitoxide/blob/main/crate-status.md#git-revision)
-  * [git-worktree](https://github.com/Byron/gitoxide/blob/main/crate-status.md#git-worktree)
   * [git-tui](https://github.com/Byron/gitoxide/blob/main/crate-status.md#git-tui)
   * [git-bundle](https://github.com/Byron/gitoxide/blob/main/crate-status.md#git-bundle)
 

git-pack/src/data/output/entry/iter_from_counts.rs

@@ -56,31 +56,20 @@ where
     );
     let (chunk_size, thread_limit, _) =
         parallel::optimize_chunk_size_and_thread_limit(chunk_size, Some(counts.len()), thread_limit, None);
-    let chunks = util::ChunkRanges::new(chunk_size, counts.len());
     {
         let progress = Arc::new(parking_lot::Mutex::new(progress.add_child("resolving")));
         progress.lock().init(None, git_features::progress::count("counts"));
         let enough_counts_present = counts.len() > 4_000;
         let start = std::time::Instant::now();
         parallel::in_parallel_if(
             || enough_counts_present,
-            chunks.clone(),
+            counts.chunks_mut(chunk_size),
             thread_limit,
             |_n| Vec::<u8>::new(),
             {
                 let progress = Arc::clone(&progress);
-                let counts = &counts;
                 let db = db.clone();
-                move |chunk_range, buf| {
-                    let chunk = {
-                        let c = &counts[chunk_range];
-                        let mut_ptr = c.as_ptr() as *mut output::Count;
-                        // SAFETY: We know that 'chunks' is only non-overlapping slices, and this function owns `counts`.
-                        #[allow(unsafe_code)]
-                        unsafe {
-                            std::slice::from_raw_parts_mut(mut_ptr, c.len())
-                        }
-                    };
+                move |chunk, buf| {
                     let chunk_size = chunk.len();
                     for count in chunk {
                         use crate::data::output::count::PackLocation::*;
@@ -135,8 +124,10 @@ where
             index
         }
     };
+
     let counts = Arc::new(counts);
     let progress = Arc::new(parking_lot::Mutex::new(progress));
+    let chunks = util::ChunkRanges::new(chunk_size, counts.len());
 
     parallel::reduce::Stepwise::new(
         chunks.enumerate(),