evolve: return the new replacement node to be stored in evolvestate While resolving phase-divergence, we can end up obsoleting the phase-divergent commit in favor of the public commit. Before this patch we return the node of public commit to store as a replacement of the phase-divergent commit. The above will not cause any problem till the time we use `hg evolve --abort` on an interrupted evolve which tries to strip the replacement nodes because it thinks that the replacements nodes are the ones which are created during the resolution and are new. Since we will be stripping a public node, `evolve --abort` will error out saying cannot strip public changeset, unable to abort evolve which is bad. We should make sure, replacements should only consist of new nodes formed. If the instablity is resolved by obsoleting in favour of old changeset, we should not store the old changeset in replacements in evolvestate.

[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