--- a/rust/hg-core/src/utils.rs	Mon Aug 30 21:18:29 2021 +0200
+++ b/rust/hg-core/src/utils.rs	Fri Sep 03 16:37:20 2021 +0200
@@ -67,36 +67,34 @@
 }
 
 pub trait SliceExt {
-    fn trim_end_newlines(&self) -> &Self;
     fn trim_end(&self) -> &Self;
     fn trim_start(&self) -> &Self;
+    fn trim_end_matches(&self, f: impl FnMut(u8) -> bool) -> &Self;
+    fn trim_start_matches(&self, f: impl FnMut(u8) -> bool) -> &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)]
-fn is_not_whitespace(c: &u8) -> bool {
-    !(*c as char).is_whitespace()
-}
+impl SliceExt for [u8] {
+    fn trim_end(&self) -> &[u8] {
+        self.trim_end_matches(|byte| byte.is_ascii_whitespace())
+    }
 
-impl SliceExt for [u8] {
-    fn trim_end_newlines(&self) -> &[u8] {
-        if let Some(last) = self.iter().rposition(|&byte| byte != b'\n') {
+    fn trim_start(&self) -> &[u8] {
+        self.trim_start_matches(|byte| byte.is_ascii_whitespace())
+    }
+
+    fn trim_end_matches(&self, mut f: impl FnMut(u8) -> bool) -> &Self {
+        if let Some(last) = self.iter().rposition(|&byte| !f(byte)) {
             &self[..=last]
         } else {
             &[]
         }
     }
-    fn trim_end(&self) -> &[u8] {
-        if let Some(last) = self.iter().rposition(is_not_whitespace) {
-            &self[..=last]
-        } else {
-            &[]
-        }
-    }
-    fn trim_start(&self) -> &[u8] {
-        if let Some(first) = self.iter().position(is_not_whitespace) {
+
+    fn trim_start_matches(&self, mut f: impl FnMut(u8) -> bool) -> &Self {
+        if let Some(first) = self.iter().position(|&byte| !f(byte)) {
             &self[first..]
         } else {
             &[]