launch_editor: refactor to use start/finish_command

The launch_editor function uses the convenient run_command_*
interface. Let's use the more flexible start_command and
finish_command functions, which will let us manipulate the
parent state while we're waiting for the child to finish.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

editor.c

@@ -37,8 +37,16 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
 
 	if (strcmp(editor, ":")) {
 		const char *args[] = { editor, path, NULL };
+		struct child_process p;
 
-		if (run_command_v_opt_cd_env(args, RUN_USING_SHELL, NULL, env))
+		memset(&p, 0, sizeof(p));
+		p.argv = args;
+		p.env = env;
+		p.use_shell = 1;
+		if (start_command(&p) < 0)
+			return error("unable to start editor '%s'", editor);
+
+		if (finish_command(&p))
 			return error("There was a problem with the editor '%s'.",
 					editor);
 	}