evolve: store the revs to be processed in the evolvestate This will help us in getting a full functional `hg evolve` where `hg evolve --continue` does not only continue one changeset.

evolve: store the replacements in the evolvestate This will greatly help when we will be implementing `hg evolve --abort`.

evolve: store the target category in evolvestate

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.

evolve: create a state object in all case Let's create a state object even when we are not in the continue mode. This will help us passing the state object to rest of the functions.

branching: merge with stable

grab: preserve phase of the grabbed changeset This patch fixes the wrong behavior of loosing secret phase of the grabbed changeset.

tests: add a test showing grabbing of secret changeset turn it into draft This patch adds a test showing wrong behavior of `hg grab` command which looses the secret phase while grabbing a secret changeset.

grab: add grab info to cmdutil.afterresolvedstates This will help us in showing how to continue the grab when user resolves all the conflicts.