This moves Driver.Size() to Differ.DiffSize(), removing the empty
implementations in devmapper and dummy, and renaming the one in aufs.
Then we fall back to a container.Changes() implementation in the non-aufs
case.
This adds 3 tests:
Verify that ChangesDirs() returns nothing when run on a copy of the
same directory.
Verify that various mutations of a directory get reported with the
right changes.
Verify that ExportChanges() + ApplyLayer() of the above mutation gets
an identical directory.
Unfortunately the last test is disabled because it fails in multiple
ways atm. But I want to get it in so that we can fix it.
This replaces the current version with the latest version from the
dm branch. Advantages in this version:
We only scan each directory tree once, which means less i/o and less chance
of container changes inbetween the two scans causing inconsistencies.
We avoid comparing some fields for change detection:
* Inode
* size-in-blocks
These can change during a copy operation (e.g. in the dummy backend)
without needing to actually reflect a change in content or metadata.
* Ctime
Any copy operation will create a new Ctime value, and there is no
API to change it to the "source" value.
* size for directories
The size of a directory doesn't have to be the same just because you
recreated the same content as another director. Internal details in
the filesystem may make these different with no "real" change.
Guillaume J. Charmes