graft: introduce --abort flag to abort interrupted graft This patch introduces a new --abort flag to `hg graft` command which aborts an interrupted graft and rollbacks to the state before graft. The behavior when some of grafted changeset get's published while interrupted graft or we have new descendants on grafted changesets is same as that of rebase which is warn the user, don't strip and abort the abort the graft. Tests are added for the new flag. .. feature:: `hg graft` now has a `--abort` flag which aborts the interrupted graft and rollbacks to state before the graft. Differential Revision: https://phab.mercurial-scm.org/D3754