From 589e0db3c53804129bf6a609500e3edb9e881b87 Mon Sep 17 00:00:00 2001
From: Martin von Zweigbergk <martinvonz@google.com>
Date: Thu, 24 Aug 2023 21:41:24 -0700
Subject: [PATCH] git_backend: remove unused proto field for resolved tree id

We store resolved tree ids in the regular Git commit, so we we never
ended up using the `resolved` variant in the `root_tree`.
---
 lib/src/git_backend.rs         | 41 +++++++++++++---------------------
 lib/src/protos/git_store.proto |  6 ++---
 lib/src/protos/git_store.rs    | 16 +++----------
 3 files changed, 21 insertions(+), 42 deletions(-)

diff --git a/lib/src/git_backend.rs b/lib/src/git_backend.rs
index c34653499..d7a575d1a 100644
--- a/lib/src/git_backend.rs
+++ b/lib/src/git_backend.rs
@@ -293,7 +293,7 @@ fn serialize_extras(commit: &Commit) -> Vec<u8> {
         uses_tree_conflict_format: commit.uses_tree_conflict_format,
         ..Default::default()
     };
-    if commit.root_tree.as_resolved().is_none() {
+    if !commit.root_tree.is_resolved() {
         assert!(commit.uses_tree_conflict_format);
         let removes = commit
             .root_tree
@@ -307,10 +307,7 @@ fn serialize_extras(commit: &Commit) -> Vec<u8> {
             .iter()
             .map(|r| r.to_bytes())
             .collect_vec();
-        let conflict = crate::protos::git_store::TreeConflict { removes, adds };
-        proto.root_tree = Some(crate::protos::git_store::commit::RootTree::Conflict(
-            conflict,
-        ));
+        proto.root_tree = Some(crate::protos::git_store::TreeConflict { removes, adds });
     }
     for predecessor in &commit.predecessors {
         proto.predecessors.push(predecessor.to_bytes());
@@ -322,26 +319,20 @@ fn deserialize_extras(commit: &mut Commit, bytes: &[u8]) {
     let proto = crate::protos::git_store::Commit::decode(bytes).unwrap();
     commit.change_id = ChangeId::new(proto.change_id);
     commit.uses_tree_conflict_format = proto.uses_tree_conflict_format;
-    match proto.root_tree {
-        Some(crate::protos::git_store::commit::RootTree::Conflict(proto_conflict)) => {
-            assert!(commit.uses_tree_conflict_format);
-            commit.root_tree = Merge::new(
-                proto_conflict
-                    .removes
-                    .iter()
-                    .map(|id_bytes| TreeId::from_bytes(id_bytes))
-                    .collect(),
-                proto_conflict
-                    .adds
-                    .iter()
-                    .map(|id_bytes| TreeId::from_bytes(id_bytes))
-                    .collect(),
-            );
-        }
-        Some(crate::protos::git_store::commit::RootTree::Resolved(_)) => {
-            panic!("found resolved root tree in extras (should only be written to git metadata)");
-        }
-        None => {}
+    if let Some(proto_conflict) = proto.root_tree {
+        assert!(commit.uses_tree_conflict_format);
+        commit.root_tree = Merge::new(
+            proto_conflict
+                .removes
+                .iter()
+                .map(|id_bytes| TreeId::from_bytes(id_bytes))
+                .collect(),
+            proto_conflict
+                .adds
+                .iter()
+                .map(|id_bytes| TreeId::from_bytes(id_bytes))
+                .collect(),
+        );
     }
     for predecessor in &proto.predecessors {
         commit.predecessors.push(CommitId::from_bytes(predecessor));
diff --git a/lib/src/protos/git_store.proto b/lib/src/protos/git_store.proto
index 67a39e5d8..450716420 100644
--- a/lib/src/protos/git_store.proto
+++ b/lib/src/protos/git_store.proto
@@ -25,10 +25,8 @@ message Commit {
   repeated bytes predecessors = 2;
   bytes change_id = 4;
 
-  oneof root_tree {
-    bytes resolved = 3;
-    TreeConflict conflict = 1;
-  }
+  // Set only for conflicts. Resolved trees are stored in the git commit
+  TreeConflict root_tree = 1;
   // TODO(#1624): delete when we assume that all commits use this format
   bool uses_tree_conflict_format = 10;
 
diff --git a/lib/src/protos/git_store.rs b/lib/src/protos/git_store.rs
index 70df97ab8..8f9fc01ca 100644
--- a/lib/src/protos/git_store.rs
+++ b/lib/src/protos/git_store.rs
@@ -13,6 +13,9 @@ pub struct Commit {
     pub predecessors: ::prost::alloc::vec::Vec<::prost::alloc::vec::Vec<u8>>,
     #[prost(bytes = "vec", tag = "4")]
     pub change_id: ::prost::alloc::vec::Vec<u8>,
+    /// Set only for conflicts. Resolved trees are stored in the git commit
+    #[prost(message, optional, tag = "1")]
+    pub root_tree: ::core::option::Option<TreeConflict>,
     /// TODO(#1624): delete when we assume that all commits use this format
     #[prost(bool, tag = "10")]
     pub uses_tree_conflict_format: bool,
@@ -22,17 +25,4 @@ pub struct Commit {
     #[deprecated]
     #[prost(bool, tag = "9")]
     pub is_pruned: bool,
-    #[prost(oneof = "commit::RootTree", tags = "3, 1")]
-    pub root_tree: ::core::option::Option<commit::RootTree>,
-}
-/// Nested message and enum types in `Commit`.
-pub mod commit {
-    #[allow(clippy::derive_partial_eq_without_eq)]
-    #[derive(Clone, PartialEq, ::prost::Oneof)]
-    pub enum RootTree {
-        #[prost(bytes, tag = "3")]
-        Resolved(::prost::alloc::vec::Vec<u8>),
-        #[prost(message, tag = "1")]
-        Conflict(super::TreeConflict),
-    }
 }