added command to copy contents of registers between each other

helix-term/src/commands.rs

@@ -440,6 +440,7 @@ impl MappableCommand {
         wclose, "Close window",
         wonly, "Close windows except current",
         select_register, "Select register",
+        copy_between_registers, "Copy contents of selected register to another",
         insert_register, "Insert register",
         align_view_middle, "Align view middle",
         align_view_top, "Align view top",
@@ -4805,6 +4806,24 @@ fn select_register(cx: &mut Context) {
     })
 }
 
+fn copy_between_registers(cx: &mut Context) {
+    // Copy from selected register to the register of the next keypress
+    let Some(values) = cx.editor.registers.read(cx.register.unwrap_or('"'), cx.editor) else {
+       return; 
+    }; 
+
+    let values: Vec<String> = values.map(|value| value.to_string()).collect();
+
+    cx.on_next_key(move |cx, event| {
+        if let Some(ch) = event.char() {
+            if let Err(err) = cx.editor.registers.write(ch, values) {
+                cx.editor.set_error(err.to_string());
+                return;
+            }
+        }
+    })
+}
+
 fn insert_register(cx: &mut Context) {
     cx.editor.autoinfo = Some(Info::from_registers(&cx.editor.registers));
     cx.on_next_key(move |cx, event| {