evolvecmd: inline _evolvemerge() into _relocatecommit() I'm about to add a version of `_relocatecommit()` that uses in-memory merge. It will be simpler to have `_evolvemerge()` inlined then than to need a separate version of that function too. Also, the name `_evolvemerge()` has often made me think that it's about evolving merge commits, so it's nice to get rid of it for that reason too.