hg.bat: return exit code explicitly for indirect invocation When "hg.bat" is invoked via interactive shell "cmd.exe" on Windows, it can store own exit code into ERRORLEVEL correctly, regardless of explicit "exit" statement in it: "cmd.exe" seems to hold ERRORLEVEL updated by the last command in the batch file (= "python hg", in "hg.bat" case). On the other hand, "hg.bat" is invoked indirectly via "subprocess.Popen" (e.g. shell alias, hooks, hgclient and so on), the parent process always receives exit code 0 from spawned "hg.bat": batch files on Windows seem not to be really spawned like as shell scripts on UNIX, but to be executed in the "cmd.exe" process. This patch returns exit code explicitly for indirect invocation. "/b" should be specified for "exit" to prevent "cmd.exe" from being terminated when "hg.bat" is invoked interactively from it.