feat: Implement From<assert:cmd::Command> for process::Command

Allows conversion with `process::Command::from(asserted_cmd)`

src/cmd.rs

@@ -18,7 +18,7 @@ use crate::output::OutputResult;
 /// [`std::process::Command`] customized for testing.
 #[derive(Debug)]
 pub struct Command {
-    cmd: process::Command,
+    pub cmd: process::Command,
     stdin: Option<bstr::BString>,
     timeout: Option<std::time::Duration>,
 }
@@ -508,6 +508,12 @@ impl From<process::Command> for Command {
     }
 }
 
+impl From<Command> for process::Command {
+    fn from(cmd: Command) -> process::Command {
+        cmd.cmd
+    }
+}
+
 impl<'c> OutputOkExt for &'c mut Command {
     fn ok(self) -> OutputResult {
         let output = self.output().map_err(OutputError::with_cause)?;