Revert "fix: make exec command decrement SHLVL correctly" (#14580)

Reverts nushell/nushell#14570

crates/nu-command/src/system/exec.rs

@@ -61,16 +61,6 @@ On Windows based systems, Nushell will wait for the command to finish and then e
         let envs = env_to_strings(engine_state, stack)?;
         command.env_clear();
         command.envs(envs);
-        // Decrement SHLVL as removing the current shell from the stack
-        // (only works in interactive mode, same as initialization)
-        if engine_state.is_interactive {
-            if let Some(shlvl) = engine_state.get_env_var("SHLVL") {
-                let shlvl = shlvl.as_int().unwrap_or(1) - 1;
-                command.env("SHLVL", shlvl.to_string());
-            } else {
-                command.env("SHLVL", "0");
-            }
-        }
 
         // Configure args.
         let args = crate::eval_arguments_from_call(engine_state, stack, call)?;

src/main.rs

@@ -325,7 +325,7 @@ fn main() -> Result<()> {
     if engine_state.is_interactive {
         let mut shlvl = engine_state
             .get_env_var("SHLVL")
-            .map(|x| x.as_int().unwrap_or(0))
+            .map(|x| x.as_str().unwrap_or("0").parse::<i64>().unwrap_or(0))
             .unwrap_or(0);
         shlvl += 1;
         engine_state.add_env_var("SHLVL".to_string(), Value::int(shlvl, Span::unknown()));