add command g to switch shell quickly (#4014)

Signed-off-by: Tw <tw19881113@gmail.com>

crates/nu-command/src/commands/shells/goto.rs

@@ -0,0 +1,51 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{CommandAction, ReturnSuccess, Signature, SyntaxShape};
+
+pub struct Goto;
+
+impl WholeStreamCommand for Goto {
+    fn name(&self) -> &str {
+        "g"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("g").required("index", SyntaxShape::Int, "the shell's index to go to")
+    }
+
+    fn usage(&self) -> &str {
+        "Go to specified shell."
+    }
+
+    fn run_with_actions(&self, args: CommandArgs) -> Result<ActionStream, ShellError> {
+        goto(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Enter the first shell",
+            example: "g 0",
+            result: None,
+        }]
+    }
+}
+
+fn goto(args: CommandArgs) -> Result<ActionStream, ShellError> {
+    Ok(ActionStream::one(ReturnSuccess::action(
+        CommandAction::GotoShell(args.req(0)?),
+    )))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Goto;
+    use super::ShellError;
+
+    #[test]
+    fn examples_work_as_expected() -> Result<(), ShellError> {
+        use crate::examples::test as test_examples;
+
+        test_examples(Goto {})
+    }
+}

crates/nu-command/src/commands/shells/mod.rs

@@ -1,11 +1,13 @@
 mod command;
 mod enter;
 mod exit;
+mod goto;
 mod next;
 mod prev;
 
 pub use command::Shells;
 pub use enter::Enter;
 pub use exit::Exit;
+pub use goto::Goto;
 pub use next::Next;
 pub use prev::Previous;

crates/nu-command/src/default_context.rs

@@ -77,6 +77,7 @@ pub fn create_default_context(interactive: bool) -> Result<EvaluationContext, Bo
             // Shells
             whole_stream_command(Next),
             whole_stream_command(Previous),
+            whole_stream_command(Goto),
             whole_stream_command(Shells),
             whole_stream_command(Enter),
             whole_stream_command(Exit),