Add logical xor operator (#7242)

We already have the binary `bit-xor` and the shortcircuiting logical
`or`(`||`) and `and`(`&&`).
This introduces `xor` as a compact form for both brevity and clarity.
You can express the operation through `not`/`and`/`or` with a slight
risk of introducing bugs through typos.

Operator precedence

`and` > `xor` > `or`

Added logic and precedence tests.

crates/nu-protocol/src/value/mod.rs

@@ -2865,6 +2865,25 @@ impl Value {
         }
     }
 
+    pub fn xor(&self, op: Span, rhs: &Value, span: Span) -> Result<Value, ShellError> {
+        match (self, rhs) {
+            (Value::Bool { val: lhs, .. }, Value::Bool { val: rhs, .. }) => Ok(Value::Bool {
+                val: (*lhs && !*rhs) || (!*lhs && *rhs),
+                span,
+            }),
+            (Value::CustomValue { val: lhs, span }, rhs) => {
+                lhs.operation(*span, Operator::Boolean(Boolean::Xor), op, rhs)
+            }
+            _ => Err(ShellError::OperatorMismatch {
+                op_span: op,
+                lhs_ty: self.get_type(),
+                lhs_span: self.span()?,
+                rhs_ty: rhs.get_type(),
+                rhs_span: rhs.span()?,
+            }),
+        }
+    }
+
     pub fn pow(&self, op: Span, rhs: &Value, span: Span) -> Result<Value, ShellError> {
         match (self, rhs) {
             (Value::Int { val: lhs, .. }, Value::Int { val: rhs, .. }) => {