evolve: add a `--abort` flag for `hg evolve` command This patch adds a new flag `--abort` to `hg evolve` command which will abort the interrupted evolve going on undoes the changes created by the evolve command till now. The changes are bookmark movements, creation of evolved commits, obsolete the old commits in favor of evolved commits. In case when user changed things while the interrupted evolve, like did some actions which created a new commit on top of evolved commits, or changed phase of evolved commits to public, the evolve fails to abort as we should not strip out the new commit formed by user neither we can strip the public changeset. The abort fails and tell user to use `hg evolve --stop` instead. Right now bookmark movement is broken, and will be fixed in upcoming patches. Tests are added for the new flag.