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>
This breaks the giant blob that was the diffApply function into two
separate parts, a differ and an applier, which results in more modular
code that should be easier to follow and easier to make any future
updates to. For example, if we want to optimize by allowing differ and
applier to run in parallel in the future, that's straightforward now.
There are also some fixes that weren't needed for MergeOp, but will be
for DiffOp, such as correctly handling the case where a deletion is
applied that is under parent directories which don't exist yet (the
correct behavior is, surprisingly, to create the parent directories as
that is what the image import/export code ends up doing).
Signed-off-by: Erik Sipsma <erik@sipsma.dev>
This consists of just the base MergeOp with support for merging LLB
results that include deletions using hardlinks as the efficient path
and copies as fallback.
Signed-off-by: Erik Sipsma <erik@sipsma.dev>
Erik Sipsma