Add ! negation support, fix POSIX exit statuses, and improve vi emulation with comprehensive tests

src/readline/register.rs

@@ -2,6 +2,24 @@ use std::{fmt::Display, sync::Mutex};
 
 pub static REGISTERS: Mutex<Registers> = Mutex::new(Registers::new());
 
+#[cfg(test)]
+pub static SAVED_REGISTERS: Mutex<Option<Registers>> = Mutex::new(None);
+
+#[cfg(test)]
+pub fn save_registers() {
+	let mut saved = SAVED_REGISTERS.lock().unwrap();
+	*saved = Some(REGISTERS.lock().unwrap().clone());
+}
+
+#[cfg(test)]
+pub fn restore_registers() {
+	let mut saved = SAVED_REGISTERS.lock().unwrap();
+	if let Some(ref registers) = *saved {
+		*REGISTERS.lock().unwrap() = registers.clone();
+	}
+	*saved = None;
+}
+
 pub fn read_register(ch: Option<char>) -> Option<RegisterContent> {
   let lock = REGISTERS.lock().unwrap();
   lock.get_reg(ch).map(|r| r.content().clone())
@@ -79,7 +97,7 @@ impl RegisterContent {
   }
 }
 
-#[derive(Default, Debug)]
+#[derive(Default, Clone, Debug)]
 pub struct Registers {
   default: Register,
   a: Register,