git-codereview: use --no-ff for sync-branch

When working with dev branches, it is possible that a branch
needed to be sync'd can be fast-forworded. For example, there is
no new commit since the last sync. Or this could happen with
multi-release-cycle branches, where we reverse-sync'd to master
for one release cycle, later try to sync master to branch for the
next cycle. Fast-forwording is generally not what we want (and it
confuses the git-codereview tool when trying to craft the CL
description). Pass --no-ff to ensure we create a merge commit.

Change-Id: Ic204882d0304ec538c2e219d34e370ba98db9374
LUCI-TryBot-Result: Go LUCI <>
Reviewed-by: Dmitri Shuralyov <>
Reviewed-by: Dmitri Shuralyov <>
diff --git a/git-codereview/sync.go b/git-codereview/sync.go
index db6650e..c60d04c 100644
--- a/git-codereview/sync.go
+++ b/git-codereview/sync.go
@@ -240,7 +240,7 @@
 		run("git", "reset", "--hard", "origin/"+parent)
 		_, err = cmdOutputErr("git", "merge", "--no-ff", "origin/"+branch)
 	} else {
-		_, err = cmdOutputErr("git", "merge", "origin/"+parent)
+		_, err = cmdOutputErr("git", "merge", "--no-ff", "origin/"+parent)
 	// Resolve codereview.cfg the right way - never take it from the merge.