Before this, there was a bug triggered under the following conditions:
1. An overlay snapshotter was being used, which caused the optimization
of preparing a new snapshot off of the base layers to be triggered
2. The base layers contained a directory that had contents
3. One subsequent layer deleted that directory w/out recreating it
4. A later layer recreated the directory
In this case, what happened was a whiteout device would be created as
part of 3 above but then in step 4 the whiteout device would be removed
and replaced with a plain directory. The problem is that such a
directory doesn't block out the files from step 2 and it doesn't know
about them because they are in a lowerdir (not the upperdir being
applied to).
The simplest fix, which this commit implements, is to just set the
directory created in step 4 as opaque, which enables the correct
behavior of blocking out files below it.
This was missed in test coverage before because tests for opaque
handling always combined 3+4 into one layer, whereas the bug requires
they be separate layers. A new integration test has been added to cover
this case.
Signed-off-by: Erik Sipsma <erik@sipsma.dev>
0a2a4fe066