localrepo: have stream_in() not modify its argument Localrepo's stream_in function modified its requirements argument. This is not good practice because it may be unexpected behavior to the caller.

localrepo: make _applyrequirements more specific Localrepo's _applyrequirements function isn't very straightforward about what it does. Its purpose is to both act as a setter for the requirements attribute, and to apply appropriate requirements to the opener's configuration. This change makes the function just focus on the latter responsibility. We rename it as such, and make setting the requirements attribute the responsibility of the caller.

localrepo: make requirements always be a set in localrepo.__init__ The init function used to create a local list, and then convert it to a set before assigning it as a data attribute. This change simplifies the function by having it always be a set, requiring no conversion.