chg: forward user-defined signals SIGUSR1 and SIGUSR2 are reserved for user-defined behaviors. They may be redefined by an hg extension [1], but cannot be easily redefined for chg. Since the default behavior (kill) is not that useful for chg, let's forward them to hg, hoping it got redefined there and could be more useful. [1] https://bitbucket.org/facebook/hg-experimental/commits/e7c883a465