Add simple cd

Cargo.lock

@@ -499,6 +499,7 @@ dependencies = [
  "glob",
  "nu-engine",
  "nu-json",
+ "nu-path",
  "nu-protocol",
  "nu-table",
  "sysinfo",

crates/nu-command/Cargo.toml

@@ -8,6 +8,7 @@ edition = "2018"
 [dependencies]
 nu-engine = { path = "../nu-engine" }
 nu-json = { path = "../nu-json" }
+nu-path = { path = "../nu-path" }
 nu-protocol = { path = "../nu-protocol" }
 nu-table = { path = "../nu-table" }
 

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;

crates/nu-protocol/src/syntax_shape.rs

@@ -86,7 +86,7 @@ impl SyntaxShape {
             SyntaxShape::Custom(custom, _) => custom.to_type(),
             SyntaxShape::Duration => Type::Duration,
             SyntaxShape::Expression => Type::Unknown,
-            SyntaxShape::FilePath => Type::FilePath,
+            SyntaxShape::FilePath => Type::String,
             SyntaxShape::Filesize => Type::Filesize,
             SyntaxShape::FullCellPath => Type::Unknown,
             SyntaxShape::GlobPattern => Type::String,