Short-hand flags (#1378)

* typo fixes

* Change signature to take in short-hand flags

* update help information

* Parse short-hand flags as their long counterparts

* lints

* Modified a couple tests to use shorthand flags

crates/nu-parser/src/parse/token_tree.rs

@@ -361,9 +361,20 @@ impl SpannedToken {
         }
     }
 
-    pub(crate) fn as_flag(&self, value: &str, source: &Text) -> Option<Flag> {
+    pub(crate) fn as_flag(&self, value: &str, short: Option<char>, source: &Text) -> Option<Flag> {
         match self.unspanned() {
-            Token::Flag(flag @ Flag { .. }) if value == flag.name().slice(source) => Some(*flag),
+            Token::Flag(flag @ Flag { .. }) => {
+                let name = flag.name().slice(source);
+                let is_long = flag.kind == FlagKind::Longhand && value == name;
+                let is_short = flag.kind == FlagKind::Shorthand
+                    && short.is_some()
+                    && short == name.chars().nth(0);
+                if is_long || is_short {
+                    Some(*flag)
+                } else {
+                    None
+                }
+            }
             _ => None,
         }
     }