refactor(cache): redesign cache system with structured keys and improved performance

- Add repo_path parameter to cached_response and cached_vec_response functions
- Implement structured cache key format with namespace, repo_path, and request proto
- Replace global cache with Moka in-memory cache using weight-based eviction
- Set 256MB memory cap with 10-minute TTL and 2-minute TTI policy
- Add metrics collection for cache operations and evictions
- Implement efficient repo-scoped invalidation using key structure
- Add detailed documentation comments explaining cache architecture
- Remove outdated dependencies and update dependency versions
- Add error handling for encoding failures in cache operations
- Optimize Vec responses with length-delimited encoding and pre-allocation

pack/pack_objects.rs

@@ -7,6 +7,8 @@ use tokio_stream::wrappers::ReceiverStream;
 use crate::bare::GitBare;
 use crate::pb::PackfileChunk;
 
+const MAX_PACK_OBJECTS_STDERR_BYTES: u64 = 64 * 1024;
+
 impl GitBare {
     /// Pack objects using git-pack-objects --stdout.
     ///
@@ -52,7 +54,15 @@ impl GitBare {
             if opts.is_some_and(|o| o.delta_base_offset) {
                 args.push("--delta-base-offset".into());
             }
-            let stdin_data = generate_pack_input(&request);
+            let stdin_data = match generate_pack_input(&request) {
+                Ok(data) => data,
+                Err(err) => {
+                    let _ = tx
+                        .send(Err(tonic::Status::invalid_argument(err.to_string())))
+                        .await;
+                    return;
+                }
+            };
 
             let mut child = match Command::new("git")
                 .args(&args)
@@ -118,7 +128,8 @@ impl GitBare {
             let stderr_task = {
                 let tx = tx.clone();
                 async move {
-                    if let Some(mut stderr) = stderr.take() {
+                    if let Some(stderr) = stderr.take() {
+                        let mut stderr = stderr.take(MAX_PACK_OBJECTS_STDERR_BYTES);
                         let mut s = String::new();
                         if stderr.read_to_string(&mut s).await.is_ok() && !s.is_empty() {
                             let _ = tx.send(Err(tonic::Status::internal(s))).await;
@@ -150,15 +161,19 @@ impl GitBare {
     }
 }
 
-fn generate_pack_input(req: &crate::pb::PackObjectsRequest) -> Vec<u8> {
+fn generate_pack_input(
+    req: &crate::pb::PackObjectsRequest,
+) -> Result<Vec<u8>, crate::error::GitError> {
     let mut input = String::new();
     if let Some(opts) = req.options.as_ref() {
         for want in &opts.wants {
+            crate::sanitize::validate_oid_hex(&want.hex)?;
             input.push_str(&format!("{}\n", want.hex));
         }
         for have in &opts.haves {
+            crate::sanitize::validate_oid_hex(&have.hex)?;
             input.push_str(&format!("^{}\n", have.hex));
         }
     }
-    input.into_bytes()
+    Ok(input.into_bytes())
 }