evolve: extract "update" code into its own function
This patch moves the code to a function which handles the case when wdir
parent is obsolete and evolve will just update to its successor.
And extraction of this to a function will also help us to fix the
issue5881.
[flake8]
ignore =
#closing bracket does not match indentation of opening bracket's line
E123,
# closing bracket does not match visual indentation
E124,
# visually indented line with same indent as next logical line
E129,
# at least two spaces before inline comment
E261,
# too many leading '#' for block comment
E266,
# expected 2 blank lines, found 0
E302,
# expected 2 blank lines after end of function or class
E305,
# module level import not at top of file
E402,
# line too long (82 > 79 characters)
E501,
# do not assign a lambda expression, use a def
E731,
# class names should use CapWords convention
N801,
# line break occurred before a binary operator
W503
builtins=xrange, execfile