Error when destination has no snapshots

[silkeh]

When running a backup with any amount of snapshots in the source but no snapshots in the destination, the program crashes with the following output:

INFO btrfs-sxbackup v0.6.7
DEBUG ['bash', '-c', 'if [ -f "/source/.btrfs-sxbackup" ]; then exit 10; fi']
DEBUG ['bash', '-c', 'cat "/source/.sxbackup/.btrfs-sxbackup"']
DEBUG ['bash', '-c', 'cat "/destination/.btrfs-sxbackup"']
INFO source :: url [/source/] container [.sxbackup/] retention [3] compress [False]
INFO destination :: url [/destination/] retention [1d:4/d, 1w:2/w, 3m:2/m, 12m:none] compress [False]
INFO preparing environment
DEBUG ['bash', '-c', 'if [ ! -d "/source/.sxbackup/" ]; then btrfs sub create "/source/.sxbackup/"; fi']
DEBUG ['bash', '-c', 'btrfs sub show "/source/.sxbackup/"']
DEBUG ['bash', '-c', 'if [ -d "/source/.sxbackup/.temp"* ]; then btrfs sub del "/source/.sxbackup/.temp"*; fi']
DEBUG ['bash', '-c', 'if [ ! -d "/destination/" ]; then btrfs sub create "/destination/"; fi']
DEBUG ['bash', '-c', 'btrfs sub show "/destination/"']
DEBUG ['bash', '-c', 'if [ -d "/destination/.temp"* ]; then btrfs sub del "/destination/.temp"*; fi']
INFO source :: retrieving snapshots
DEBUG ['bash', '-c', 'btrfs sub list -o "/source/.sxbackup/"']
INFO destination :: retrieving snapshots
DEBUG ['bash', '-c', 'btrfs sub list -o "/destination/"']
ERROR list index out of range
ERROR Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/btrfs_sxbackup/__main__.py", line 216, in main
    job.run()
  File "/usr/local/lib/python3.4/dist-packages/btrfs_sxbackup/core.py", line 971, in run
    and self.source.snapshots[0].name.timestamp != self.destination.snapshots[0].name.timestamp:
IndexError: list index out of range

In case of an empty destination a full snapshot should probably be transferred, in which case the check for a non-matching snapshot should be modified.

[masc3d]

btrfs-sxbackup always tries to preserve the most recent snapshot when cleaning out but yes, it makes sense to support it in case the destination dies. thanks for reporting.