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- Remove outdated dependencies and update dependency versions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

diff/get_diff.rs

@@ -22,10 +22,15 @@ struct RawDiffEntry {
 /// Type alias for diff raw output: (entries, numstat_map)
 type DiffRawOutput = (Vec<RawDiffEntry>, HashMap<String, (u32, u32, bool)>);
 
+const MAX_DIFF_COMMAND_OUTPUT_BYTES: usize = 64 * 1024 * 1024;
+
 impl GitBare {
     pub fn get_diff(&self, request: GetDiffRequest) -> GitResult<GetDiffResponse> {
         let base = match request.base.and_then(|s| s.selector) {
-            Some(crate::pb::object_selector::Selector::Oid(oid)) => oid.hex.clone(),
+            Some(crate::pb::object_selector::Selector::Oid(oid)) => {
+                crate::sanitize::validate_oid_hex(&oid.hex)?;
+                oid.hex.clone()
+            }
             Some(crate::pb::object_selector::Selector::Revision(name)) => {
                 crate::sanitize::validate_revision(&name.revision)?;
                 name.revision.clone()
@@ -33,7 +38,10 @@ impl GitBare {
             None => "HEAD".into(),
         };
         let head = match request.head.and_then(|s| s.selector) {
-            Some(crate::pb::object_selector::Selector::Oid(oid)) => oid.hex.clone(),
+            Some(crate::pb::object_selector::Selector::Oid(oid)) => {
+                crate::sanitize::validate_oid_hex(&oid.hex)?;
+                oid.hex.clone()
+            }
             Some(crate::pb::object_selector::Selector::Revision(name)) => {
                 crate::sanitize::validate_revision(&name.revision)?;
                 name.revision.clone()
@@ -48,6 +56,11 @@ impl GitBare {
         );
 
         let options = request.options.as_ref();
+        if let Some(options) = options {
+            for path in &options.pathspec {
+                crate::sanitize::validate_file_path(path)?;
+            }
+        }
         let want_patch = options.is_some_and(|o| o.include_patch);
 
         let (raw_entries, numstat_map) = self.diff_raw_and_numstat(&base, &head, options)?;
@@ -177,6 +190,11 @@ impl GitBare {
                 stderr: String::from_utf8_lossy(&result.stderr).into_owned(),
             });
         }
+        if result.stdout.len() > MAX_DIFF_COMMAND_OUTPUT_BYTES {
+            return Err(GitError::InvalidArgument(format!(
+                "diff metadata output too large (max {MAX_DIFF_COMMAND_OUTPUT_BYTES} bytes)"
+            )));
+        }
 
         // Split by NUL — each record is NUL-terminated
         let records: Vec<&[u8]> = result.stdout.split(|b| *b == 0).collect();
@@ -343,6 +361,11 @@ impl GitBare {
                 stderr: String::from_utf8_lossy(&result.stderr).into_owned(),
             });
         }
+        if result.stdout.len() > MAX_DIFF_COMMAND_OUTPUT_BYTES {
+            return Err(GitError::InvalidArgument(format!(
+                "diff patch output too large (max {MAX_DIFF_COMMAND_OUTPUT_BYTES} bytes)"
+            )));
+        }
 
         // Split combined patch output by "diff --git" headers
         let mut map = HashMap::new();