nu-cli refactor moving commands into their own crate nu-command (#2910)

* move commands, futures.rs, script.rs, utils

* move over maybe_print_errors

* add nu_command crate references to nu_cli

* in commands.rs open up to pub mod from pub(crate)

* nu-cli, nu-command, and nu tests are now passing

* cargo fmt

* clean up nu-cli/src/prelude.rs

* code cleanup

* for some reason lex.rs was not formatted, may be causing my error

* remove mod completion from lib.rs which was not being used along with quickcheck macros

* add in allow unused imports

* comment out one failing external test; comment out one failing internal test

* revert commenting out failing tests; something else might be going on; someone with a windows machine should check and see what is going on with these failing windows tests

* Update Cargo.toml

Extend the optional features to nu-command

Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>

crates/nu-command/tests/commands/enter.rs

@@ -0,0 +1,85 @@
+use nu_test_support::fs::{files_exist_at, Stub::EmptyFile};
+use nu_test_support::nu;
+use nu_test_support::playground::Playground;
+use std::path::Path;
+
+#[test]
+fn knows_the_filesystems_entered() {
+    Playground::setup("enter_test_1", |dirs, sandbox| {
+        sandbox
+            .within("red_pill")
+            .with_files(vec![
+                EmptyFile("andres.nu"),
+                EmptyFile("jonathan.nu"),
+                EmptyFile("yehuda.nu"),
+            ])
+            .within("blue_pill")
+            .with_files(vec![
+                EmptyFile("bash.nxt"),
+                EmptyFile("korn.nxt"),
+                EmptyFile("powedsh.nxt"),
+            ])
+            .mkdir("expected");
+
+        let red_pill_dir = dirs.test().join("red_pill");
+        let blue_pill_dir = dirs.test().join("blue_pill");
+        let expected = dirs.test().join("expected");
+        let expected_recycled = expected.join("recycled");
+
+        nu!(
+            cwd: dirs.test(),
+            r#"
+                enter expected
+                mkdir recycled
+                enter ../red_pill
+                mv jonathan.nu ../expected
+                enter ../blue_pill
+                cp *.nxt ../expected/recycled
+                p
+                p
+                mv ../red_pill/yehuda.nu .
+                n
+                mv andres.nu ../expected/andres.nu
+                exit
+                cd ..
+                rm red_pill --recursive
+                exit
+                n
+                rm blue_pill --recursive
+                exit
+            "#
+        );
+
+        assert!(!red_pill_dir.exists());
+        assert!(files_exist_at(
+            vec![
+                Path::new("andres.nu"),
+                Path::new("jonathan.nu"),
+                Path::new("yehuda.nu"),
+            ],
+            expected
+        ));
+
+        assert!(!blue_pill_dir.exists());
+        assert!(files_exist_at(
+            vec![
+                Path::new("bash.nxt"),
+                Path::new("korn.nxt"),
+                Path::new("powedsh.nxt"),
+            ],
+            expected_recycled
+        ));
+    })
+}
+
+#[test]
+fn errors_if_file_not_found() {
+    Playground::setup("enter_test_2", |dirs, _| {
+        let actual = nu!(
+            cwd: dirs.test(),
+            "enter i_dont_exist.csv"
+        );
+
+        assert!(actual.err.contains("Cannot find file"));
+    })
+}