Add simple cd

crates/nu-command/src/default_context.rs

@@ -16,6 +16,7 @@ pub fn create_default_context() -> Rc<RefCell<EngineState>> {
         working_set.add_decl(Box::new(Alias));
         working_set.add_decl(Box::new(Benchmark));
         working_set.add_decl(Box::new(BuildString));
+        working_set.add_decl(Box::new(Cd));
         working_set.add_decl(Box::new(Def));
         working_set.add_decl(Box::new(Do));
         working_set.add_decl(Box::new(Each));

crates/nu-command/src/filesystem/cd.rs

@@ -0,0 +1,46 @@
+use nu_engine::CallExt;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, SyntaxShape, Value};
+
+pub struct Cd;
+
+impl Command for Cd {
+    fn name(&self) -> &str {
+        "cd"
+    }
+
+    fn usage(&self) -> &str {
+        "Change directory."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("cd").optional("path", SyntaxShape::FilePath, "the path to change to")
+    }
+
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let path: Option<String> = call.opt(context, 0)?;
+
+        let path = match path {
+            Some(path) => {
+                let path = nu_path::expand_tilde(path);
+                path.to_string_lossy().to_string()
+            }
+            None => {
+                let path = nu_path::expand_tilde("~");
+                path.to_string_lossy().to_string()
+            }
+        };
+        let _ = std::env::set_current_dir(&path);
+
+        //FIXME: this only changes the current scope, but instead this environment variable
+        //should probably be a block that loads the information from the state in the overlay
+        context.add_env_var("PWD".into(), path);
+        Ok(Value::Nothing { span: call.head })
+    }
+}

crates/nu-command/src/filesystem/mod.rs

@@ -1,3 +1,5 @@
+mod cd;
 mod ls;
 
+pub use cd::Cd;
 pub use ls::Ls;