cross-platform backup tool Alpha Release v2.1.1a0 a lot under the hood

Hello,

This is an alpha release so that many people can test new features. All 
changes are documented in the changelog 
<https://github.com/rdiff-backup/rdiff-backup/blob/v2.1.1a0/CHANGELOG.adoc#new-in-v2-1-1a0>, 
but despite 12 fixes and 3 smaller new features, the main changes are 
under the hood, heavily restructuring the code to simplify it and 
introduce concepts of plugins. We've also converted all documentation 
from markdown to asciidoc <https://asciidoctor.org/> because it's 
standardized 
<https://projects.eclipse.org/projects/asciidoc.asciidoc-lang>, has more 
features and looks nicer once rendered.

Please use this release to test and report issues, especially regarding:

   * usage in client/server in combination with version v2.0.5 of
     rdiff-backup
   * usage under Windows (and MacOS/X)

It's an alpha version, everything might change, disappear and/or fail, 
do *NOT* get in love with a specific feature and do *NOT* use this 
version for production.

The installation procedure hasn't changed much and is available from the 
readme 
<https://github.com/rdiff-backup/rdiff-backup/blob/v2.1.1a0/README.adoc> 
(alpha packages might or might not be offered by the maintainers, in 
doubt install via |pip install rdiff-backup==2.1.1a0| under Linux and 
use the attached binaries under Windows). You might want to use the 
side-by-side installation 
<https://github.com/rdiff-backup/rdiff-backup/blob/v2.1.1a0/docs/migration.adoc#side-by-side-installation> 
to safeguard your productive installation.

—

This release has 19 assets:

   * rdiff-backup-2.1.1a0.tar.gz
   * rdiff-backup-2.1.1a0.win32exe.zip
   * rdiff-backup-2.1.1a0.win64exe.zip
   * 
rdiff_backup-2.1.1a0-cp36-cp36m-manylinux_2_12_i686.manylinux2010_i686.whl
   * 
rdiff_backup-2.1.1a0-cp36-cp36m-manylinux_2_12_x86_64.manylinux2010_x86_64.whl
   * 
rdiff_backup-2.1.1a0-cp36-cp36m-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
   * 
rdiff_backup-2.1.1a0-cp37-cp37m-manylinux_2_12_i686.manylinux2010_i686.whl
   * 
rdiff_backup-2.1.1a0-cp37-cp37m-manylinux_2_12_x86_64.manylinux2010_x86_64.whl
   * 
rdiff_backup-2.1.1a0-cp37-cp37m-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
   * 
rdiff_backup-2.1.1a0-cp38-cp38-manylinux_2_12_i686.manylinux2010_i686.whl
   * 
rdiff_backup-2.1.1a0-cp38-cp38-manylinux_2_12_x86_64.manylinux2010_x86_64.whl
   * 
rdiff_backup-2.1.1a0-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
   * 
rdiff_backup-2.1.1a0-cp39-cp39-manylinux_2_12_i686.manylinux2010_i686.whl
   * 
rdiff_backup-2.1.1a0-cp39-cp39-manylinux_2_12_x86_64.manylinux2010_x86_64.whl
   * 
rdiff_backup-2.1.1a0-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
   * rdiff_backup-2.1.1a0-cp39-cp39-win32.whl
   * rdiff_backup-2.1.1a0-cp39-cp39-win_amd64.whl
   * Source code (zip)
   * Source code (tar.gz)

Visit the release page 
<https://github.com/rdiff-backup/rdiff-backup/releases/tag/v2.1.1a0> to 
download them.

Kind Regards, Eric