scmstore: add utility method for converting StoreTree to manifest-tree::Entry

Summary: Adds a utility method for converting a `StoreTree` to a `manifest-tree::Entry`, which wraps an hg manifest blob and provides methods for parsing it as a tree manifest (and a `TryFrom` impl used to convert it to a pre-parsed `manifest::List`, which is used by BackingStore in the next change in this stack).

Reviewed By: andll

Differential Revision: D30859470

fbshipit-source-id: 411e80a14861e0739b0c398290055002b35e59d3

eden/scm/lib/revisionstore/Cargo.toml

@@ -26,6 +26,7 @@ http-client = { path = "../http-client" }
 indexedlog = { path = "../indexedlog" }
 lfs_protocol = { path = "../../../mononoke/lfs_protocol" }
 lz4-pyframe = { path = "../lz4-pyframe" }
+manifest-tree = { path = "../manifest-tree" }
 memmap = "0.7"
 mincode = { path = "../mincode" }
 minibytes = { path = "../minibytes", features = ["frombytes"] }

eden/scm/lib/revisionstore/src/scmstore/tree/types/lazy_tree.rs

@@ -9,7 +9,7 @@ use anyhow::Result;
 use tracing::instrument;
 
 use edenapi_types::TreeEntry;
-
+use manifest_tree::TreeEntry as ManifestTreeEntry;
 use minibytes::Bytes;
 use types::{HgId, Key};
 
@@ -72,4 +72,9 @@ impl LazyTree {
             ContentStore(_, _) => None,
         })
     }
+
+    pub fn manifest_tree_entry(&mut self) -> Result<ManifestTreeEntry> {
+        // TODO(meyer): Make manifest-tree crate use minibytes::Bytes
+        Ok(ManifestTreeEntry(self.hg_content()?.into_vec().into()))
+    }
 }

eden/scm/lib/revisionstore/src/scmstore/tree/types/store_tree.rs

@@ -7,6 +7,10 @@
 
 use std::ops::BitOr;
 
+use anyhow::{anyhow, Result};
+
+use manifest_tree::TreeEntry as ManifestTreeEntry;
+
 use crate::scmstore::{
     tree::types::{LazyTree, TreeAttributes},
     value::StoreValue,
@@ -17,6 +21,15 @@ pub struct StoreTree {
     pub(crate) content: Option<LazyTree>,
 }
 
+impl StoreTree {
+    pub fn manifest_tree_entry(&mut self) -> Result<ManifestTreeEntry> {
+        self.content
+            .as_mut()
+            .ok_or_else(|| anyhow!("no content available"))?
+            .manifest_tree_entry()
+    }
+}
+
 impl StoreValue for StoreTree {
     type Attrs = TreeAttributes;
 
@@ -50,6 +63,7 @@ impl Default for StoreTree {
         StoreTree { content: None }
     }
 }
+
 impl From<LazyTree> for StoreTree {
     fn from(v: LazyTree) -> Self {
         StoreTree { content: Some(v) }