Add --reverse option

When restoring data from a backup the source and the destination repositories are logically swapped over the creation case. That is, if you backed up your data from /snapshots to /backup, for instance, you would restore it from /backup to /snapshots. This behavior is logical and intuitive. However, sometimes it is more easily to have the program deal with this swapping of the parameters in order to not have to create an entirely new command line with these two parameters reversed. For that matter, this change introduces the --reverse option that essentially swaps the source and the destination repository. Note that although not intended, the newly introduced option can also be used in the non-restore case, i.e., when creating a new snapshot in the source directory and synchronizing it with a destination repository.

Author: d-e-s-o

btrfs-backup/README.md

@@ -51,3 +51,15 @@ To restore the latest snapshot for the given subvolume from the backup,
 the following command can be used:
 
 ``$ btrfs-backup --restore --subvolume=subvolume/ backup/ snapshots/``
+
+Alternatively, you can use the --reverse option to keep the order of the
+source and destination repository that was used during backup (as
+opposed to restoration). This option exists for convenience only, so
+that not the entire command line has to be amended but rather two
+options can be appended to convert a backup operation into a restore
+operation.
+
+```
+$ btrfs-backup --subvolume=subvolume/ snapshots/ backup/ --restore
+ --reverse
+```

btrfs-backup/src/deso/btrfs/main.py

@@ -19,6 +19,9 @@
 
 """The main module interfaces with the user input and sets up bits required for execution."""
 
+from deso.btrfs.alias import (
+ alias,
+)
 from sys import (
  stderr,
 )
@@ -87,6 +90,10 @@ def main(argv):
  "This option triggers the opposite behavior to what is done by "
  "default.",
  )
+ parser.add_argument(
+ "--reverse", action="store_true", dest="reverse", default=False,
+ help="Reverse (i.e., swap) the source and destination repositories.",
+ )
  parser.add_argument(
  "-s", "--subvolume", action="append", metavar="subvolume", nargs=1,
  dest="subvolumes", required=True,
@@ -101,8 +108,15 @@ def main(argv):
  # Note that argv contains the path to the program as the first element
  # which we kindly ignore.
  namespace = parser.parse_args(argv[1:])
- # The namespace's subvolumes are stored as a list of list of strings.
- # Convert it to a list of strings.
- subvolumes = [x for x, in namespace.subvolumes]
- return run(subvolumes, namespace.src, namespace.dst,
- restore=namespace.restore)
+
+ with alias(namespace) as ns:
+ # The namespace's subvolumes are stored as a list of list of
+ # strings. Convert it to a list of strings.
+ subvolumes = [x for x, in ns.subvolumes]
+
+ if ns.reverse:
+ src_repo, dst_repo = ns.dst, ns.src
+ else:
+ src_repo, dst_repo = ns.src, ns.dst
+
+ return run(subvolumes, src_repo, dst_repo, restore=ns.restore)

btrfs-backup/src/deso/btrfs/test/testMain.py

@@ -78,9 +78,16 @@ def backup():
  """Invoke the program to backup snapshots/subvolumes."""
  run(m.path("snapshots"), b.path("backup"))
 
- def restore():
+ def restore(*options, reverse=False):
  """Invoke the program to restore snapshots/subvolumes."""
- run(b.path("backup"), m.path("snapshots"), "--restore")
+ if not reverse:
+ src = b.path("backup")
+ dst = m.path("snapshots")
+ else:
+ src = m.path("snapshots")
+ dst = b.path("backup")
+
+ run(src, dst, "--restore", *options)
 
  with alias(self._mount) as m:
  # We backup our data to a different btrfs volume.
@@ -113,6 +120,19 @@ def restore():
  self.assertContains(m.path(user, "data", "movie.mp4"), "abcdefgh")
  self.assertContains(m.path(root, ".ssh", "key.pub"), "1234567890")
 
+ # Case 3) Once again delete all snapshots but this time
+ # restore them in conjunction with the --reverse
+ # option.
+ wipeSubvolumes(m.path("snapshots"))
+
+ # This time we use the '--reverse' option.
+ restore("--reverse", reverse=True)
+
+ user, root = glob(m.path("snapshots", "*"))
+
+ self.assertContains(m.path(user, "data", "movie.mp4"), "abcdefgh")
+ self.assertContains(m.path(root, ".ssh", "key.pub"), "1234567890")
+
 
 if __name__ == "__main__":
  main()