git-assembler 1.2

Improved worktree support thanks to Etienne Laurin:

* Allow to create staging branches even when the base branch is already
  checked out in a different worktree.
* Fix internal state paths when using worktrees.

General bug fixes:

* Fix dirty graph state/coloring when using ``base`` and merging with
  the base branch itself.
* Read correctly assembly files with a missing EOL (thanks to
  Etienne Laurin).
* Handle checkout errors without a spurious traceback when referring to
  undefined branches.

Minor improvements:

* Remove useless commit error messages when performing a rerere
  autocommit.