Merge branch 'master' into core-updates

gnu: rdup: Fix tests.

* gnu/packages/backup.scm (rdup) [arguments]: Add pre-check phase.
  [origin]: Add snippet.

Merge branch 'master' into core-updates

gnu: Move libarchive to (gnu packages backup).

* gnu/packages/compression.scm (libarchive): Move to...
* gnu/packages/backup.scm (libarchive): ... here.
  Import (guix licenses) with #:renamer to avoid conflicting 'zlib'
  bindings.

gnu: Add rdiff-backup.

* gnu/packages/backup.scm (rdiff-backup): New variable.

gnu: Add btar.

* gnu/packages/backup.scm (btar): New variable.

gnu: Add rdup.

* gnu/packages/backup.scm (rdup): New variable.

gnu: Add hdup.

* gnu/packages/backup.scm (hdup): New variable.

Merge branch 'master' into core-updates

gnu: Add duplicity.

* gnu/packages/backup.scm: New file.
* gnu-system.am: Add it.