view: move creation of initial operation to OpHeadsStore

This is a step towards getting rid of
`MutableView::update_op_heads()`.

lib/src/op_heads_store.rs

@@ -24,6 +24,7 @@ use crate::view;
 use std::path::PathBuf;
 use std::sync::Arc;
 
+use crate::store::CommitId;
 use thiserror::Error;
 
 /// Manages the very set of current heads of the operation log. The store is
@@ -40,8 +41,25 @@ pub enum OpHeadResolutionError {
 }
 
 impl OpHeadsStore {
-    pub fn init(dir: PathBuf) -> Self {
+    pub fn init(
-        OpHeadsStore { dir }
+        dir: PathBuf,
+        op_store: &Arc<dyn OpStore>,
+        checkout: CommitId,
+    ) -> (Self, OperationId, op_store::View) {
+        let mut root_view = op_store::View::new(checkout.clone());
+        root_view.head_ids.insert(checkout);
+        let root_view_id = op_store.write_view(&root_view).unwrap();
+        let operation_metadata = OperationMetadata::new("initialize repo".to_string());
+        let init_operation = op_store::Operation {
+            view_id: root_view_id,
+            parents: vec![],
+            metadata: operation_metadata,
+        };
+        let init_operation_id = op_store.write_operation(&init_operation).unwrap();
+
+        let op_heads_store = OpHeadsStore { dir };
+        op_heads_store.add_op_head(&init_operation_id);
+        (op_heads_store, init_operation_id, root_view)
     }
 
     pub fn load(dir: PathBuf) -> OpHeadsStore {

lib/src/view.rs

@@ -219,27 +219,16 @@ impl ReadonlyView {
         path: PathBuf,
         checkout: CommitId,
     ) -> Self {
-        let mut root_view = op_store::View::new(checkout.clone());
-        root_view.head_ids.insert(checkout);
-        let root_view_id = op_store.write_view(&root_view).unwrap();
-        let operation_metadata = OperationMetadata::new("initialize repo".to_string());
-        let init_operation = op_store::Operation {
-            view_id: root_view_id,
-            parents: vec![],
-            metadata: operation_metadata,
-        };
-        let init_operation_id = op_store.write_operation(&init_operation).unwrap();
-
         let op_heads_dir = path.join("op_heads");
         std::fs::create_dir(&op_heads_dir).unwrap();
-        let op_heads_store = Arc::new(OpHeadsStore::init(op_heads_dir));
+        let (op_heads_store, init_op_id, root_view) =
-        op_heads_store.add_op_head(&init_operation_id);
+            OpHeadsStore::init(op_heads_dir, &op_store, checkout);
 
         ReadonlyView {
             store,
             op_store,
-            op_heads_store,
+            op_heads_store: Arc::new(op_heads_store),
-            op_id: init_operation_id,
+            op_id: init_op_id,
             index_store,
             data: root_view,
         }