graft: make --force apply across continues (issue3220) Since --force determines the list of revisions to be grafted, it doesn't really make sense for users to have to keep typing --force --continue as they continue grafting.

workingfilectx.date = (1000, 0)
ASCII   : Gr?ezi!
Latin-1 : Gr�ezi!
UTF-8   : Grüezi!
(['foo'], [], [], [], [], [], [])
diff --git a/foo b/foo

--- a/foo
+++ b/foo
@@ -1,1 +1,2 @@
 foo
+bar