avoid infinite recursion in matcher.
avoid infinite recursion in matcher.

after sync (or sync --local), clean up repository:
	* look for and close CLs submitted on our behalf
	* remove unmodified files from CLs
	* warn about empty CLs

R=r
http://go/go-review/1017029

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go