Get ready for 0.21.4 release

Get ready for 0.21.3 release

Get ready for 0.21.2 release

Get ready for 0.21.1 release

Get ready to release 0.21.0

Get ready to release 0.20.3

Get ready to release 0.20.2

tests: fix deprecation warning

Get ready to release v0.20.0

Release 0.19.1

API changes:

- Rename Commit._message to Commit.raw_message
- Rename Signature._name to Signature.raw_name
- Rename Signature._email to Signature.raw_email

New features:

- Remote.push(refspec)
- Tag.get_object()

And some bugs fixed.

Thanks to Brodie Rao, Fraser Tweedale, Andrew Chin and Carlos Martín
Nieto.