Fix utils/execute.rs windows support

Fix utils/execute.rs windows support so that on windows when we don't
have signals to worry about, we don't. But when we are on unix systems
that do have signals we do handle them.

This relates to issue #235.

Signed-off-by: Drew De Ponte <cyphactor@gmail.com>

[changelog]
fixed: execute external command support for windows

<!-- ps-id: 242e7637-266a-4bd8-b47e-359d6dd40dbc -->

src/ps/private/utils/execute.rs

@@ -3,7 +3,7 @@ use std::io;
 use std::os::unix::process::ExitStatusExt;
 #[cfg(target_family = "windows")]
 use std::os::windows::process::ExitStatusExt;
-use std::process::{Command, Output};
+use std::process::{Command, ExitStatus, Output};
 use std::result::Result;
 
 #[derive(Debug)]
@@ -15,6 +15,19 @@ pub enum ExecuteError {
     ExitMissingSignal, // triggered when we understand exit to be triggered by signal but no signal found
 }
 
+#[cfg(target_family = "unix")]
+fn handle_error_no_code(status: ExitStatus) -> ExecuteError {
+    match status.signal() {
+        Some(signal) => ExecuteError::ExitSignal(signal),
+        None => ExecuteError::ExitMissingSignal,
+    }
+}
+
+#[cfg(target_family = "windows")]
+fn handle_error_no_code(_: ExitStatus) -> ExecuteError {
+    return ExecuteError::ExitMissingSignal;
+}
+
 /// Execute an external command in the foreground allowing it to take over the
 /// terminal while waiting for the external application to complete with an
 /// exit status.
@@ -27,13 +40,10 @@ pub fn execute(exe: &str, args: &[&str]) -> Result<(), ExecuteError> {
                 if status.success() {
                     Ok(())
                 } else {
-                    match status.code() {
-                        Some(code) => Err(ExecuteError::ExitStatus(code)),
-                        None => match status.signal() {
-                            Some(signal) => Err(ExecuteError::ExitSignal(signal)),
-                            None => Err(ExecuteError::ExitMissingSignal),
-                        },
-                    }
+                    Err(match status.code() {
+                        Some(code) => ExecuteError::ExitStatus(code),
+                        None => handle_error_no_code(status),
+                    })
                 }
             }
         },