commit: add --force-close-branch flag to close a non-head changeset While closing branch from a changeset which is not a branch head current implementation abort this action in every case but, there can be the situations where the changeset is not a local head but could be a remote head. This patch adds the functionality to bypass the "abort: can only close branch heads" by introducing --force-close-branch flag. Test case changes demonstrate the new functionality added. Differential Revision: https://phab.mercurial-scm.org/D6490