Need to save a VERSION metadata file with a backup

[jeremymv2]

As features make it into the Chef Server it has become obvious that we need a better way to handle data and API changes in ec-backup based on the version of the Chef Server the backup was made from.

For example, a backup of a Chef Server version 12.1.0 will have subtle differences that a backup made of a 12.15.x server. A restore of the 12.1.0 backup to a current Chef Server release will need certain corrective behavior in order to restore in a way that handles all of the differences in the current releases. A specific example is the renaming of the ORG_global_admins to ::brewinc_read_access_group and the addition of the ::server-admins group.

If we save a VERSION file with the knife-ec-backup backup archive, we can then utilize that file to determine the version of the Chef Server the backup was made from and the version of knife-ec-backup that was used.

Knowing those versions, we can then create a cleaner implementation to handle data modification during a restore.

[jeremymv2]

Once a VERSION file exists, @stevendanna has proposed a plan of attack moving forward.

It's raised in this thread.

[jeremymv2]

@stevendanna a thought occurred to me that because of the --only-org ORG option, a plausible scenario might exist where different ORGs were backed up with different versions of ec-backup.

While pointing this out, I still think that we should just write the VERSION file at the root of the backup dir and assume users will always re-run a backup of a specific org after changing the gem version, before they try a restore.