Consistently replace line-endings in paste/replace commands

Previously we replaced line-endings in pasted text to the document
line-ending for some values in paste commands. We missed the `repeat`
values in paste though and didn't do any replacement in the replace
command.

Along with this change I've refactored the replace command to avoid
intermediary collections. We previously eagerly collected the values
from the input register as a `Vec<String>` but we can avoid both of
those conversions and only allocate for the conversion to a `Tendril`.
We can also switch from `str::repeat` to a manual implementation to
avoid the intermediary conversion to a String - this avoids an extra
allocation in the common case (i.e. no count).

Fixes helix-editor#12329

helix-term/src/commands.rs

@@ -4401,6 +4401,8 @@ enum Paste {
     Cursor,
 }
 
+static LINE_ENDING_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"\r\n|\r|\n").unwrap());
+
 fn paste_impl(
     values: &[String],
     doc: &mut Document,
@@ -4417,26 +4419,26 @@ fn paste_impl(
         doc.append_changes_to_history(view);
     }
 
-    let repeat = std::iter::repeat(
-        // `values` is asserted to have at least one entry above.
-        values
-            .last()
-            .map(|value| Tendril::from(value.repeat(count)))
-            .unwrap(),
-    );
-
     // if any of values ends with a line ending, it's linewise paste
     let linewise = values
         .iter()
         .any(|value| get_line_ending_of_str(value).is_some());
 
-    // Only compiled once.
-    static REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"\r\n|\r|\n").unwrap());
-    let mut values = values
-        .iter()
-        .map(|value| REGEX.replace_all(value, doc.line_ending.as_str()))
-        .map(|value| Tendril::from(value.as_ref().repeat(count)))
-        .chain(repeat);
+    let map_value = |value| {
+        let value = LINE_ENDING_REGEX.replace_all(value, doc.line_ending.as_str());
+        let mut out = Tendril::from(value.as_ref());
+        for _ in 1..count {
+            out.push_str(&value);
+        }
+        out
+    };
+
+    let repeat = std::iter::repeat(
+        // `values` is asserted to have at least one entry above.
+        map_value(values.last().unwrap()),
+    );
+
+    let mut values = values.iter().map(|value| map_value(value)).chain(repeat);
 
     let text = doc.text();
     let selection = doc.selection(view.id);
@@ -4533,19 +4535,24 @@ fn replace_with_yanked_impl(editor: &mut Editor, register: char, count: usize) {
     else {
         return;
     };
-    let values: Vec<_> = values.map(|value| value.to_string()).collect();
     let scrolloff = editor.config().scrolloff;
+    let (view, doc) = current_ref!(editor);
 
-    let (view, doc) = current!(editor);
-    let repeat = std::iter::repeat(
-        values
-            .last()
-            .map(|value| Tendril::from(&value.repeat(count)))
-            .unwrap(),
-    );
-    let mut values = values
-        .iter()
-        .map(|value| Tendril::from(&value.repeat(count)))
+    let map_value = |value: &Cow<str>| {
+        let value = LINE_ENDING_REGEX.replace_all(value, doc.line_ending.as_str());
+        let mut out = Tendril::from(value.as_ref());
+        for _ in 1..count {
+            out.push_str(&value);
+        }
+        out
+    };
+    let mut values_rev = values.rev().peekable();
+    // `values` is asserted to have at least one entry above.
+    let last = values_rev.peek().unwrap();
+    let repeat = std::iter::repeat(map_value(last));
+    let mut values = values_rev
+        .rev()
+        .map(|value| map_value(&value))
         .chain(repeat);
     let selection = doc.selection(view.id);
     let transaction = Transaction::change_by_selection(doc.text(), selection, |range| {
@@ -4555,7 +4562,9 @@ fn replace_with_yanked_impl(editor: &mut Editor, register: char, count: usize) {
             (range.from(), range.to(), None)
         }
     });
+    drop(values);
 
+    let (view, doc) = current!(editor);
     doc.apply(&transaction, view.id);
     doc.append_changes_to_history(view);
     view.ensure_cursor_in_view(doc, scrolloff);