refactor(build): reformat code and add tonic health dependency

- Reformatted build script with proper indentation and line breaks
- Added tonic-health dependency to Cargo.toml and updated lock file
- Improved error handling in disk cache with concurrent deletion checks
- Refactored conditional chains using && and let expressions
- Reformatted struct initialization and function parameter lists
- Added proper spacing and alignment in language stats processing
- Improved assertion formatting in test cases
- Reorganized import statements and code layout in multiple files
- Updated metrics functions with better parameter handling and formatting

disk_cache.rs

@@ -271,10 +271,8 @@ impl DiskCache {
         }
         let start = std::time::Instant::now();
         let path = self.cache_file_path(namespace, digest);
-        if !path.exists() {
-            crate::metrics::record_cache_op("disk", "miss", start.elapsed());
-            return Ok(None);
-        }
+
+        // Check expiry before reading, but handle concurrent deletion gracefully.
         if let Ok(metadata) = std::fs::metadata(&path)
             && let Ok(modified) = metadata.modified()
             && let Ok(age) = SystemTime::now().duration_since(modified)
@@ -292,16 +290,26 @@ impl DiskCache {
             crate::metrics::record_cache_op("disk", "expired", start.elapsed());
             return Ok(None);
         }
-        let data = std::fs::read(&path).map_err(GitError::Io)?;
-        tracing::debug!(
-            namespace = %namespace,
-            digest = %digest,
-            size = data.len(),
-            elapsed_ms = start.elapsed().as_millis() as u64,
-            "cache hit"
-        );
-        crate::metrics::record_cache_op("disk", "hit", start.elapsed());
-        Ok(Some(data))
+
+        match std::fs::read(&path) {
+            Ok(data) => {
+                tracing::debug!(
+                    namespace = %namespace,
+                    digest = %digest,
+                    size = data.len(),
+                    elapsed_ms = start.elapsed().as_millis() as u64,
+                    "cache hit"
+                );
+                crate::metrics::record_cache_op("disk", "hit", start.elapsed());
+                Ok(Some(data))
+            }
+            Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
+                // File was deleted between metadata check and read — treat as miss.
+                crate::metrics::record_cache_op("disk", "miss", start.elapsed());
+                Ok(None)
+            }
+            Err(e) => Err(GitError::Io(e)),
+        }
     }
 
     /// Insert a cached response for the given namespace and digest.
@@ -338,9 +346,8 @@ impl DiskCache {
             return Ok(None);
         }
         let path = self.cache_file_path(namespace, digest);
-        if !path.exists() {
-            return Ok(None);
-        }
+
+        // Check expiry; handle concurrent deletion gracefully.
         if let Ok(metadata) = std::fs::metadata(&path)
             && let Ok(modified) = metadata.modified()
             && let Ok(age) = SystemTime::now().duration_since(modified)
@@ -349,8 +356,12 @@ impl DiskCache {
             std::fs::remove_file(&path).ok();
             return Ok(None);
         }
-        let file = std::fs::File::open(&path).map_err(GitError::Io)?;
-        Ok(Some(file))
+
+        match std::fs::File::open(&path) {
+            Ok(file) => Ok(Some(file)),
+            Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(None),
+            Err(e) => Err(GitError::Io(e)),
+        }
     }
 
     /// Open a cache file for streaming write.