evolve: add an `--update` flag to `hg evolve` command This patch adds a new `--update` flag which defaults to True. The update flag updates the working directory to the head of evolved revisions after `hg evolve` command. This flag can be used to not update your working directory after `hg evolve` which has been one of the biggest feature request from fig team at Google. To not update your working directory, the user can do `hg evolve --no-update`. If the working directory get obsoleted by evolve command, it will update to the successor. This patch also adds some basic tests for the flag introduced.

tests: add tests for testing --abort while content-divergence resolution This patch adds a new test file with a very basic test of `--abort` on an interrupted evolve which was resolving content-divergence. Upcoming patches will add more rigourous tests.

evolve: fix storage of replacements and temprevs node in evolvestate The _completephaseivergent() was not respecting rules on how to store the new node ids created in evolvestate. The rules are: * store the temporary relocated commits in temprevs * store the final new commit in replacements This patch make sure we follow the above rules and also use the return value returned by _resolvephasedivergence(). The tests change demonstrates that we are all good now.