* support for worktrees

* fix(cygwin): use ``cygpath.exe`` to convert *Windows* paths and respect

different mount-points (e.g. *MSYS2* which is a *Cygwin* clone mounts drives

under root).

2.1.3 - Bugfixes

* The `GIT_DIR` environment variable does not override the `path` argument when

initializing a `Repo` object anymore. However, if said `path` unset, `GIT_DIR`

will be used to fill the void.

All issues and PRs can be viewed in all detail when following this URL:

https://github.com/gitpython-developers/GitPython/issues?q=is%3Aclosed+milestone%3A%22v2.1.0+-+proper+windows+support%22

2.0.7 - New Features

* `IndexFile.commit(...,skip_hooks=False)` added. This parameter emulates the

behaviour of `--no-verify` on the command-line.

2.0.6 - Fixes and Features

commit messages contained ``\r`` characters

* Fix: progress handler exceptions are not caught anymore, which would usually just hide bugs

previously.

* Fix: The `Git.execute` method will now redirect `stdout` to `devnull` if `with_stdout` is false,

which is the intended behaviour based on the parameter's documentation.

2.0.2 - Fixes