feat(core): implement Git repository operations with gRPC services

- Add advertise_refs functionality for Git protocol communication
- Implement archive service with TAR/ZIP format support and streaming
- Create blame service for Git file annotation with line tracking
- Add branch management including create, delete, rename and compare operations
- Implement merge checking with conflict detection and fast-forward handling
- Add cherry-pick functionality for applying commits between branches
- Integrate gix library for Git repository operations and object handling
- Add comprehensive test suite covering all Git operations
- Implement proper error handling and repository validation
- Add pagination support for large result sets
- Create protobuf definitions for all Git operations and data structures
- Add build system for gRPC code generation and dependency management

paginate.rs

@@ -0,0 +1,46 @@
+use crate::pb::{PageInfo, Pagination};
+
+/// Simple offset-based pagination over an in-memory slice.
+/// The `page_token` is a decimal string encoding the start offset.
+pub fn paginate<T: Clone>(items: &[T], pagination: Option<&Pagination>) -> (Vec<T>, PageInfo) {
+    let page_size = pagination
+        .map(|p| p.page_size as usize)
+        .unwrap_or(items.len().max(1))
+        .max(1);
+
+    let start_offset = pagination
+        .and_then(|p| {
+            if p.page_token.is_empty() {
+                None
+            } else {
+                p.page_token.parse::<usize>().ok()
+            }
+        })
+        .unwrap_or(0)
+        .min(items.len());
+
+    let end = std::cmp::min(start_offset + page_size, items.len());
+    let has_next = end < items.len();
+    let next_page_token = if has_next {
+        end.to_string()
+    } else {
+        String::new()
+    };
+
+    (
+        items[start_offset..end].to_vec(),
+        PageInfo {
+            next_page_token,
+            has_next_page: has_next,
+            total_count: items.len() as u64,
+        },
+    )
+}
+
+/// Apply sort direction. Ascending = no-op (preserves order).
+/// Descending reverses the slice.
+pub fn apply_sort<T>(items: &mut [T], sort_direction: i32) {
+    if sort_direction == crate::pb::SortDirection::Desc as i32 {
+        items.reverse();
+    }
+}