evolvecmd: use the evolvestate object passed as argument in _solveunstable
Earlier if get a merge conflict, we used to initialize a new evolvestate object
and used to save it. Let's start using the state object which we get in as
argument as that will contain more data about the state.
evolvecmd: pass evolvestate object to _solve* functions
This patchs adds an argument evolvestate to _solve* functions. This will help us
in having one evolvestate object which we can pass around various functions and
keep storing what's going on.