diff -r 2e5dd18d6dc3 -r a25033eb43b5 rust/hg-core/src/utils.rs
--- a/rust/hg-core/src/utils.rs	Mon Feb 08 23:08:44 2021 +0100
+++ b/rust/hg-core/src/utils.rs	Mon Feb 08 23:41:58 2021 +0100
@@ -67,6 +67,7 @@
     fn trim_start(&self) -> &Self;
     fn trim(&self) -> &Self;
     fn drop_prefix(&self, needle: &Self) -> Option<&Self>;
+    fn split_2(&self, separator: u8) -> Option<(&[u8], &[u8])>;
 }
 
 #[allow(clippy::trivially_copy_pass_by_ref)]
@@ -116,6 +117,13 @@
             None
         }
     }
+
+    fn split_2(&self, separator: u8) -> Option<(&[u8], &[u8])> {
+        let mut iter = self.splitn(2, |&byte| byte == separator);
+        let a = iter.next()?;
+        let b = iter.next()?;
+        Some((a, b))
+    }
 }
 
 pub trait Escaped {