hgpatch: do not use hg exit status
hgpatch: do not use hg exit status

Fixes issue 2243.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5146041

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang