feat(revset): use hints to optimize binary revset evals

Now that we can pass revsets around to limit how many commits a rhs examines
during it's evaluation, this change actually starts passing such hints, but
only for `intersection()` and `difference()`.

This is a crude approach, of course, but it gets the job done and it
significantly improves performance for `intersection()` and `difference()`.

Author: claytonrcarter

git-branchless-revset/src/builtins.rs

@@ -94,7 +94,7 @@ fn fn_none(ctx: &mut Context, name: &str, args: &[Expr], _: &Option<&CommitSet>)
 
 #[instrument]
 fn fn_union(ctx: &mut Context, name: &str, args: &[Expr], _: &Option<&CommitSet>) -> EvalResult {
-    let (lhs, rhs) = eval2(ctx, name, args)?;
+    let (lhs, rhs) = eval2(ctx, name, args, false)?;
     Ok(lhs.union(&rhs))
 }
 
@@ -105,7 +105,7 @@ fn fn_intersection(
     args: &[Expr],
     _: &Option<&CommitSet>,
 ) -> EvalResult {
-    let (lhs, rhs) = eval2(ctx, name, args)?;
+    let (lhs, rhs) = eval2(ctx, name, args, true)?;
     Ok(lhs.intersection(&rhs))
 }
 
@@ -116,19 +116,19 @@ fn fn_difference(
     args: &[Expr],
     _: &Option<&CommitSet>,
 ) -> EvalResult {
-    let (lhs, rhs) = eval2(ctx, name, args)?;
+    let (lhs, rhs) = eval2(ctx, name, args, true)?;
     Ok(lhs.difference(&rhs))
 }
 
 #[instrument]
 fn fn_only(ctx: &mut Context, name: &str, args: &[Expr], _: &Option<&CommitSet>) -> EvalResult {
-    let (lhs, rhs) = eval2(ctx, name, args)?;
+    let (lhs, rhs) = eval2(ctx, name, args, false)?;
     Ok(ctx.dag.query_only(lhs, rhs)?)
 }
 
 #[instrument]
 fn fn_range(ctx: &mut Context, name: &str, args: &[Expr], _: &Option<&CommitSet>) -> EvalResult {
-    let (lhs, rhs) = eval2(ctx, name, args)?;
+    let (lhs, rhs) = eval2(ctx, name, args, false)?;
     Ok(ctx.dag.query_range(lhs, rhs)?)
 }
 

git-branchless-revset/src/eval.rs

@@ -310,11 +310,12 @@ pub(super) fn eval2(
     ctx: &mut Context,
     function_name: &str,
     args: &[Expr],
+    limit_rhs: bool,
 ) -> Result<(CommitSet, CommitSet), EvalError> {
     match args {
         [lhs, rhs] => {
             let lhs = eval_inner(ctx, lhs, &None)?;
-            let rhs = eval_inner(ctx, rhs, &None)?;
+            let rhs = eval_inner(ctx, rhs, &limit_rhs.then_some(&lhs))?;
             Ok((lhs, rhs))
         }
 
@@ -507,6 +508,76 @@ mod tests {
             "###);
         }
 
+        {
+            let expr = Expr::FunctionCall(
+                Cow::Borrowed("intersection"),
+                vec![
+                    Expr::Name(Cow::Owned(test1_oid.to_string())),
+                    Expr::Name(Cow::Owned(test2_oid.to_string())),
+                ],
+            );
+            insta::assert_debug_snapshot!(eval_and_sort(&effects, &repo, &mut dag, &expr), @r###"
+            Ok(
+                [],
+            )
+            "###);
+
+            let expr = Expr::FunctionCall(
+                Cow::Borrowed("intersection"),
+                vec![
+                    Expr::Name(Cow::Owned(test1_oid.to_string())),
+                    Expr::Name(Cow::Owned(test1_oid.to_string())),
+                ],
+            );
+            insta::assert_debug_snapshot!(eval_and_sort(&effects, &repo, &mut dag, &expr), @r###"
+            Ok(
+                [
+                    Commit {
+                        inner: Commit {
+                            id: 62fc20d2a290daea0d52bdc2ed2ad4be6491010e,
+                            summary: "create test1.txt",
+                        },
+                    },
+                ],
+            )
+            "###);
+        }
+
+        {
+            let expr = Expr::FunctionCall(
+                Cow::Borrowed("difference"),
+                vec![
+                    Expr::Name(Cow::Owned(test1_oid.to_string())),
+                    Expr::Name(Cow::Owned(test2_oid.to_string())),
+                ],
+            );
+            insta::assert_debug_snapshot!(eval_and_sort(&effects, &repo, &mut dag, &expr), @r###"
+            Ok(
+                [
+                    Commit {
+                        inner: Commit {
+                            id: 62fc20d2a290daea0d52bdc2ed2ad4be6491010e,
+                            summary: "create test1.txt",
+                        },
+                    },
+                ],
+            )
+            "###);
+
+            let expr = Expr::FunctionCall(
+                Cow::Borrowed("difference"),
+                vec![
+                    Expr::Name(Cow::Owned(test1_oid.to_string())),
+                    Expr::Name(Cow::Owned(test1_oid.to_string())),
+                ],
+            );
+            insta::assert_debug_snapshot!(eval_and_sort(&effects, &repo, &mut dag, &expr), @r###"
+            Ok(
+                [],
+            )
+            "###);
+        }
+
         {
             let expr = Expr::FunctionCall(
                 Cow::Borrowed("siblings"),