Log Message:
Update to 2.6.0. From the changelog:

- **NEW** Allow keeping manual commits while squashing all wip commits
  by finishing a mob-session with `mob done --squash-wip`.
- Removed experimental command `mob squash-wip` in favor of new `mob
  done --squash-wip`.
- Added missing configuration option `MOB_WIP_BRANCH_PREFIX` for
  `.mob` file.