mu-file-utils: add run_command0

To ensure command ran and had exit-code=0 in one go.

lib/utils/mu-utils-file.cc

@@ -162,7 +162,7 @@ Mu::runtime_path(Mu::RuntimePath path, const std::string& muhome)
 		throw std::logic_error("unknown path");
 	}
 }
-
+/* LCOV_EXCL_START*/
 static gpointer
 cancel_wait(gpointer data)
 {
@@ -210,7 +210,7 @@ Mu::g_cancellable_new_with_timeout(guint timeout)
 
 	return cancel;
 }
-
+/* LCOV_EXCL_STOP*/
 
 Result<std::string>
 Mu::read_from_stdin()
@@ -286,6 +286,18 @@ Mu::run_command(std::initializer_list<std::string> args, bool try_setsid)
 				to_string_gchar(std::move(std_err/*consumed*/))});
 }
 
+Result<Mu::CommandOutput>
+Mu::run_command0(std::initializer_list<std::string> args, bool try_setsid)
+{
+	if (auto&& res{run_command(args, try_setsid)}; !res)
+		return res;
+	else if (res->exit_code != 0)
+		return Err(Error::Code::File, "command ran with non-zero exit code");
+	else
+		return Ok(std::move(*res));
+}
+
+
 Mu::Option<std::string>
 Mu::program_in_path(const std::string& name)
 {

lib/utils/mu-utils-file.hh

@@ -227,14 +227,14 @@ Result<std::string> make_temp_dir();
 Result<void> remove_directory(const std::string& path);
 
 /**
- * Run some system command
+ * Run some system command.
  *
  * @param args a list of commmand line arguments (like argv)
  * @param try_setsid whether to try setsid(2) (see its manpage for details) if this
  *        system supports it.
  *
- * @return Ok(exit code) or an error. Note that exit-code != 0 is _not_
- * considered an error from the perspective of this function.
+ * @return Ok(exit code) or an error. Note that exit-code != 0 is _not_ considered an error from the
+ * perspective of run_command, but is for run_command0
  */
 struct CommandOutput {
 	int exit_code;
@@ -243,6 +243,8 @@ struct CommandOutput {
 };
 Result<CommandOutput> run_command(std::initializer_list<std::string> args,
 				  bool try_setsid=false);
+Result<CommandOutput> run_command0(std::initializer_list<std::string> args,
+				   bool try_setsid=false);
 
 /**
  * Try to 'play' (ie., open with it's associated program) a file. On MacOS, the