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

error.rs

@@ -0,0 +1,78 @@
+pub type GitResult<T> = Result<T, GitError>;
+
+#[derive(Debug, thiserror::Error)]
+pub enum GitError {
+    #[error("repository is not bare")]
+    NotBareRepository,
+    #[error("git command failed with status {status_code:?}: {stderr}")]
+    CommandFailed {
+        status_code: Option<i32>,
+        stderr: String,
+    },
+    #[error("unsafe git command rejected: {0}")]
+    UnsafeCommand(String),
+    #[error("object not found: {0}")]
+    ObjectNotFound(String),
+    #[error("reference not found: {0}")]
+    RefNotFound(String),
+    #[error("parse error: {0}")]
+    ParseError(String),
+    #[error(transparent)]
+    Io(#[from] std::io::Error),
+    #[error("gix error: {0}")]
+    Gix(String),
+    #[error("repository not found")]
+    RepoNotFound,
+    #[error("internal error: {0}")]
+    Internal(String),
+    #[error("not found: {0}")]
+    NotFound(String),
+    #[error("invalid oid: {0}")]
+    InvalidOid(String),
+    #[error("locked: {0}")]
+    Locked(String),
+    #[error("permission denied: {0}")]
+    PermissionDenied(String),
+    #[error("authentication failed: {0}")]
+    AuthFailed(String),
+    #[error("payload too large: {0}")]
+    PayloadTooLarge(String),
+    #[error("invalid argument: {0}")]
+    InvalidArgument(String),
+}
+
+macro_rules! impl_gix_error {
+    ($err_type:path) => {
+        impl From<$err_type> for GitError {
+            fn from(e: $err_type) -> Self {
+                GitError::Gix(e.to_string())
+            }
+        }
+    };
+}
+
+impl_gix_error!(gix::object::find::existing::Error);
+impl_gix_error!(gix::object::find::existing::with_conversion::Error);
+impl_gix_error!(gix::object::find::Error);
+impl_gix_error!(gix::reference::iter::Error);
+impl_gix_error!(gix::reference::iter::init::Error);
+impl_gix_error!(gix::reference::find::existing::Error);
+impl_gix_error!(gix::reference::find::Error);
+impl_gix_error!(gix::reference::head_id::Error);
+impl_gix_error!(gix::repository::merge_bases_many::Error);
+impl_gix_error!(gix::reference::peel::Error);
+impl_gix_error!(gix::repository::blame_file::Error);
+impl_gix_error!(gix::blame::Error);
+impl_gix_error!(gix::revision::walk::Error);
+impl_gix_error!(gix::revision::walk::iter::Error);
+impl_gix_error!(gix::revision::spec::parse::single::Error);
+impl_gix_error!(gix::open::Error);
+impl_gix_error!(gix::objs::decode::Error);
+impl_gix_error!(gix::date::Error);
+impl_gix_error!(gix::repository::diff_tree_to_tree::Error);
+
+impl From<Box<dyn std::error::Error + Send + Sync>> for GitError {
+    fn from(e: Box<dyn std::error::Error + Send + Sync>) -> Self {
+        GitError::Gix(e.to_string())
+    }
+}