git-codereview: set GIT_GOFMT_HOOK=off for sync-branch

When doing a merge, it's unlikely that someone
would want to run gofmt for files they didn't
edit, so turn that off by default.

Change-Id: I6c95b866740d5deda575feda256eee35dba3d9d1
Reviewed-on: https://go-review.googlesource.com/c/review/+/320269
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/git-codereview/sync.go b/git-codereview/sync.go
index b079c84..2d93bcb 100644
--- a/git-codereview/sync.go
+++ b/git-codereview/sync.go
@@ -125,7 +125,8 @@
 }
 
 func cmdSyncBranch(args []string) {
-	os.Setenv("GIT_EDITOR", ":") // do not bring up editor during merge, commit
+	os.Setenv("GIT_EDITOR", ":")       // do not bring up editor during merge, commit
+	os.Setenv("GIT_GOFMT_HOOK", "off") // do not require gofmt during merge
 
 	var cont, mergeBackToParent bool
 	flags.BoolVar(&cont, "continue", false, "continue after merge conflicts")