[PATCH experimental-tests] erofs-utils: tests: add test for rebuild fulldata

[Gao Xiang]

Hi Lucas,

On 2026/4/18 04:06, Lucas Karpinski wrote:
> Add a regression test for building a self-contained image out of two other
> erofs images.
> 
> 1. Create img1 & img2 with various file types and sizes.
> 2. Rebuild a new self-contained image of img1 & img2.
> 3. Delete img1 & img2 to prove that this isn't use the blob based rebuild
>     path.
> 4. Mount the new self-contained image and compare the checksum to the
>     original folders.

Thanks for the patch. I wonder if it's possible to:
  1) Use a common dataset as the base layer (see other existing tests);
  2) Mount two overlayfs to get the incremental layers;
     - one to generate some artifacial dirs, files;
     - the other to change/delete some files, or delete dirs, new another
       dirs;
  3) Test typical metadata (whiteout, opaque), and data with:
     a) fsmerged erofs;
     b) overlayfs mount;
     fssum those two mounts.

Thanks,
Gao Xiang