Support paths including .. in inputs

[ola-rozenfeld]

Currently, we translate an input of "a/b/../foo" to a tree containing only a/foo. Ideally, it would be nice to translate it to a tree which also includes the a/b directory, even though it is not "really" used, because the bot would expect that.
Note: this would require #42 plus empty directories support on the server side as well.