lazymanifest: make __iter__ generate filenames, not 3-tuples...
lazymanifest: make __iter__ generate filenames, not 3-tuples
The _lazymanifest type(s) behave very much like a sorted dict with
filenames as keys and (nodeid, flags) as values. It therefore seems
surprising that its __iter__ generates 3-tuples of (path, nodeid,
flags). Let's make it match dict's behavior of generating the keys
instead, and add a new iterentries method for the 3-tuples. With this
change, the "x" in "if x in lm" and "for x in lm" now have the same
type (a filename string).
