diff --git a/lib/src/default_index/revset_engine.rs b/lib/src/default_index/revset_engine.rs
index 7b0a79db1b..a9609944c7 100644
--- a/lib/src/default_index/revset_engine.rs
+++ b/lib/src/default_index/revset_engine.rs
@@ -1142,7 +1142,8 @@ fn has_diff_from_parent(
             return Ok(false);
         }
     }
-    let from_tree = rewrite::merge_commit_trees_without_repo(store, &index, &parents)?;
+    let from_tree =
+        rewrite::merge_commit_trees_no_resolve_without_repo(store, &index, &parents)?.resolve()?;
     let to_tree = commit.tree()?;
     let mut tree_diff = from_tree.diff_stream(&to_tree, matcher);
     async {
@@ -1163,7 +1164,8 @@ fn matches_diff_from_parent(
     files_matcher: &dyn Matcher,
 ) -> BackendResult<bool> {
     let parents: Vec<_> = commit.parents().try_collect()?;
-    let from_tree = rewrite::merge_commit_trees_without_repo(store, &index, &parents)?;
+    let from_tree =
+        rewrite::merge_commit_trees_no_resolve_without_repo(store, &index, &parents)?.resolve()?;
     let to_tree = commit.tree()?;
     let tree_diff = from_tree.diff_stream(&to_tree, files_matcher);
     // Conflicts are compared in materialized form. Alternatively, conflict
diff --git a/lib/src/merged_tree.rs b/lib/src/merged_tree.rs
index f83acf77ad..e5c053beab 100644
--- a/lib/src/merged_tree.rs
+++ b/lib/src/merged_tree.rs
@@ -301,17 +301,23 @@ impl MergedTree {
         }
     }
 
-    /// Merges this tree with `other`, using `base` as base.
+    /// Merges this tree with `other`, using `base` as base. Any conflicts will
+    /// be resolved recursively if possible.
     pub fn merge(&self, base: &MergedTree, other: &MergedTree) -> BackendResult<MergedTree> {
+        self.merge_no_resolve(base, other).resolve()
+    }
+
+    /// Merges this tree with `other`, using `base` as base, without attempting
+    /// to resolve file conflicts.
+    pub fn merge_no_resolve(&self, base: &MergedTree, other: &MergedTree) -> MergedTree {
         let nested = Merge::from_vec(vec![
             self.trees.clone(),
             base.trees.clone(),
             other.trees.clone(),
         ]);
-        let flattened = MergedTree {
+        MergedTree {
             trees: nested.flatten().simplify(),
-        };
-        flattened.resolve()
+        }
     }
 }
 
diff --git a/lib/src/rewrite.rs b/lib/src/rewrite.rs
index 5e6f913a65..3a58defefc 100644
--- a/lib/src/rewrite.rs
+++ b/lib/src/rewrite.rs
@@ -33,13 +33,19 @@ use crate::repo_path::RepoPath;
 use crate::settings::UserSettings;
 use crate::store::Store;
 
+/// Merges `commits` and tries to resolve any conflicts recursively.
 #[instrument(skip(repo))]
 pub fn merge_commit_trees(repo: &dyn Repo, commits: &[Commit]) -> BackendResult<MergedTree> {
-    merge_commit_trees_without_repo(repo.store(), repo.index(), commits)
+    if let [commit] = commits {
+        commit.tree()
+    } else {
+        merge_commit_trees_no_resolve_without_repo(repo.store(), repo.index(), commits)?.resolve()
+    }
 }
 
+/// Merges `commits` without attempting to resolve file conflicts.
 #[instrument(skip(index))]
-pub fn merge_commit_trees_without_repo(
+pub fn merge_commit_trees_no_resolve_without_repo(
     store: &Arc<Store>,
     index: &dyn Index,
     commits: &[Commit],
@@ -58,9 +64,10 @@ pub fn merge_commit_trees_without_repo(
                 .iter()
                 .map(|id| store.get_commit(id))
                 .try_collect()?;
-            let ancestor_tree = merge_commit_trees_without_repo(store, index, &ancestors)?;
+            let ancestor_tree =
+                merge_commit_trees_no_resolve_without_repo(store, index, &ancestors)?;
             let other_tree = other_commit.tree()?;
-            new_tree = new_tree.merge(&ancestor_tree, &other_tree)?;
+            new_tree = new_tree.merge_no_resolve(&ancestor_tree, &other_tree);
         }
         Ok(new_tree)
     }