End/Beginning of current arg motion, or keyword arg text object

[ashiklom]

I deal with a lot of keyword arguments, so it would be great to have one (or both!) of two things:

(1) A motion to move to the end/beginning of the current argument. For example:

myfunction(arg1 = |some_object, arg2 = another_object)
# (evil-end-of-arg)
myfunction(arg1 = some_object|, arg2 = another_object)

(2) A text object for the current keyword argument expression. Capital "A" might work well for mapping this. For example:

# Let "A" be mapped to evil-keyword-arg text object
myfunction(arg1 = som|e_object, arg2 = another_object)
# ciA
myfunction(arg1 = |, arg2 = another_object)