From ff25e6a6ff8d4ee81df825145a5ea0261bd80f43 Mon Sep 17 00:00:00 2001
From: Philip Metzger <philipmetzger@bluewin.ch>
Date: Thu, 6 Jul 2023 23:57:24 +0200
Subject: [PATCH] revsets: Add `descendants_at` and `ancestors_at`

They are needed for `next` and `prev`.
They behave symmetrically for parents and children.
---
 lib/src/revset.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/lib/src/revset.rs b/lib/src/revset.rs
index b854844f96..d1a0562ac0 100644
--- a/lib/src/revset.rs
+++ b/lib/src/revset.rs
@@ -380,6 +380,15 @@ impl RevsetExpression {
         })
     }
 
+    /// Ancestors of `self`, including `self` up to `generation` back.
+    pub fn ancestors_at(self: &Rc<RevsetExpression>, generation: u64) -> Rc<RevsetExpression> {
+        Rc::new(RevsetExpression::Ancestors {
+            heads: self.clone(),
+            generation: generation..(generation + 1),
+            is_legacy: false,
+        })
+    }
+
     /// Children of `self`.
     pub fn children(self: &Rc<RevsetExpression>) -> Rc<RevsetExpression> {
         Rc::new(RevsetExpression::Descendants {
@@ -405,6 +414,15 @@ impl RevsetExpression {
         })
     }
 
+    /// Descendants of `self`, including `self` up to `generation` back.
+    pub fn descendants_at(self: &Rc<RevsetExpression>, generation: u64) -> Rc<RevsetExpression> {
+        Rc::new(RevsetExpression::Descendants {
+            roots: self.clone(),
+            generation: (generation - 1)..generation,
+            is_legacy: false,
+        })
+    }
+
     /// Commits that are descendants of `self` and ancestors of `heads`, both
     /// inclusive.
     pub fn dag_range_to(