Add the default help flag

crates/nu-protocol/src/signature.rs

@@ -54,6 +54,16 @@ impl Eq for Signature {}
 
 impl Signature {
     pub fn new(name: impl Into<String>) -> Signature {
+        // default help flag
+        let flag = Flag {
+            long: "help".into(),
+            short: Some('h'),
+            arg: None,
+            desc: "Display this help message".into(),
+            required: false,
+            var_id: None,
+        };
+
         Signature {
             name: name.into(),
             usage: String::new(),
@@ -61,7 +71,7 @@ impl Signature {
             required_positional: vec![],
             optional_positional: vec![],
             rest_positional: None,
-            named: vec![],
+            named: vec![flag],
             is_filter: false,
             creates_scope: false,
         }

crates/nu-protocol/src/span.rs

@@ -10,7 +10,7 @@ where
     pub span: Span,
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
 pub struct Span {
     pub start: usize,
     pub end: usize,
@@ -37,6 +37,10 @@ impl Span {
             end: self.end - offset,
         }
     }
+
+    pub fn contains(&self, pos: usize) -> bool {
+        pos >= self.start && pos < self.end
+    }
 }
 
 pub fn span(spans: &[Span]) -> Span {

crates/nu-protocol/tests/test_signature.rs

@@ -31,10 +31,13 @@ fn test_signature_chained() {
 
     assert_eq!(signature.required_positional.len(), 1);
     assert_eq!(signature.optional_positional.len(), 1);
-    assert_eq!(signature.named.len(), 3);
+    assert_eq!(signature.named.len(), 4); // The 3 above + help
     assert!(signature.rest_positional.is_some());
-    assert_eq!(signature.get_shorts(), vec!['r', 'n']);
-    assert_eq!(signature.get_names(), vec!["req_named", "named", "switch"]);
+    assert_eq!(signature.get_shorts(), vec!['h', 'r', 'n']);
+    assert_eq!(
+        signature.get_names(),
+        vec!["help", "req_named", "named", "switch"]
+    );
     assert_eq!(signature.num_positionals(), 2);
 
     assert_eq!(