feat(tvix/store/directorysvc): add put_multiple_start

This provides a handle to upload multiple proto::Directory as part of
the same closure.

Change-Id: I9213dde257a260c8622239918ea541064b270484
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8356
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>

tvix/store/src/directoryservice/memory.rs

@@ -4,6 +4,7 @@ use std::collections::HashMap;
 use std::sync::{Arc, RwLock};
 use tracing::{instrument, warn};
 
+use super::utils::SimplePutter;
 use super::{DirectoryService, DirectoryTraverser};
 
 #[derive(Clone, Default)]
@@ -74,4 +75,14 @@ impl DirectoryService for MemoryDirectoryService {
     fn get_recursive(&self, root_directory_digest: &[u8; 32]) -> Self::DirectoriesIterator {
         DirectoryTraverser::with(self.clone(), root_directory_digest)
     }
+
+    type DirectoryPutter = SimplePutter<Self>;
+
+    #[instrument(skip_all)]
+    fn put_multiple_start(&self) -> Self::DirectoryPutter
+    where
+        Self: Clone,
+    {
+        SimplePutter::new(self.clone())
+    }
 }