Compressed repositories
=======================

Backup and restore with compression
-----------------------------------

Compressed backups should work just like normal ones, except with all
the data written to the repository being compressed. We thus repeat a
basic backup test, but with compression.

    SCENARIO backup simple data using compression
    GIVEN 100kB of new data in directory L
    AND a manifest of L in M
    AND user U sets configuration compress-with to deflate
    WHEN user U backs up directory L to repository R
    AND user U restores their latest generation in repository R into X
    THEN L, restored to X, matches manifest M
    AND user U can fsck the repository R

If this works, everything else should work as well: by the time Obnam
writes anything to the repository, it has lost its sparseness, or
other special filesystem characteristics, and it's just B-tree nodes
or chunk data.

It should be possible to restore from a compressed repository, even
without turning compression on. We continue the test scenario
accordingly.

    GIVEN user U sets configuration compress-with to none
    WHEN user U restores their latest generation in repository R into Y
    THEN L, restored to Y, matches manifest M
    AND user U can fsck the repository R

We would also like to turn compression on after not using it, without
having to do any extra work. This requires a new scenario.

    SCENARIO enable compression later
    GIVEN 100kB of new data in directory L
    WHEN user U backs up directory L to repository R

Then enable compression, add some more data, and backup again. The
result should now be verifiable.

    GIVEN user U sets configuration compress-with to deflate
    AND 100kB of new data in directory L
    AND a manifest of L in M
    WHEN user U backs up directory L to repository R
    AND user U restores their latest generation in repository R into X
    THEN L, restored to X, matches manifest M
    AND user U can fsck the repository R

Using both compression and encryption
-------------------------------------

We need to be able to combine compression with encryption. Let's do
the test again, with new options.

    SCENARIO backup simple data using compression and encryption
    GIVEN 100kB of new data in directory L
    AND a manifest of L in M
    AND user U sets configuration compress-with to deflate
    GIVEN user U uses encryption key "Test Key One" from test-data/keyring-1
    WHEN user U backs up directory L to repository R
    AND user U restores their latest generation in repository R into X
    THEN L, restored to X, matches manifest M
    AND user U can fsck the repository R