From c058ffeed767c1dc194f4e51a792e44049ccfe4d Mon Sep 17 00:00:00 2001
From: Martin von Zweigbergk <martinvonz@google.com>
Date: Tue, 7 Dec 2021 22:14:44 -0800
Subject: [PATCH] rewrite: avoid accessing `MutRepo::view()` when rebasing
 descendants

Since 94e03f5ac859, we lazily filter out non-heads from `View`'s set
of head. Accessing the `MutRepo::view()` triggers that filtering. This
patch makes `DescendantRebaser` not unnecessarily do that. That speeds
up the rebasing of 162 descendants in the git.git repo from ~3.6 s to
~330 ms. Rebasing 1272 descendants takes ~885 ms.
---
 lib/src/repo.rs    | 4 ++++
 lib/src/rewrite.rs | 5 ++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/src/repo.rs b/lib/src/repo.rs
index 7cccabe9a..801ba2a57 100644
--- a/lib/src/repo.rs
+++ b/lib/src/repo.rs
@@ -528,6 +528,10 @@ impl MutableRepo {
         )
     }
 
+    pub fn get_checkout(&mut self) -> CommitId {
+        self.view.borrow().checkout().clone()
+    }
+
     pub fn set_checkout(&mut self, id: CommitId) {
         self.view_mut().set_checkout(id);
     }
diff --git a/lib/src/rewrite.rs b/lib/src/rewrite.rs
index 03acee381..c519af45c 100644
--- a/lib/src/rewrite.rs
+++ b/lib/src/rewrite.rs
@@ -264,7 +264,7 @@ impl<'settings, 'repo> DescendantRebaser<'settings, 'repo> {
     }
 
     fn update_references(&mut self, old_commit_id: CommitId, new_commit_ids: Vec<CommitId>) {
-        if *self.mut_repo.view().checkout() == old_commit_id {
+        if self.mut_repo.get_checkout() == old_commit_id {
             // We arbitrarily pick a new checkout among the candidates.
             let new_commit_id = new_commit_ids[0].clone();
             let new_commit = self.mut_repo.store().get_commit(&new_commit_id).unwrap();
@@ -272,10 +272,9 @@ impl<'settings, 'repo> DescendantRebaser<'settings, 'repo> {
         }
 
         if let Some(branch_names) = self.branches.get(&old_commit_id) {
-            let view = self.mut_repo.view();
             let mut branch_updates = vec![];
             for branch_name in branch_names {
-                let local_target = view.get_local_branch(branch_name).unwrap();
+                let local_target = self.mut_repo.get_local_branch(branch_name).unwrap();
                 for old_add in local_target.adds() {
                     if old_add == old_commit_id {
                         branch_updates.push((branch_name.clone(), true));