Blobs in persistent tiles are not versioned / versioning content with blobs in persistent tiles result empty blobs in version history

[datakurre]

Each CMFEditions' version of a content with persistent tiles with blobs, will create a new empty blob into filesystem for each found blob. E.g. with persistent image tile, a new version will result one empty blob for the image blob itself and another for its imagescale blob.

This should be fixed by implementing a such new modifier for CMFEditions, which would somehow handle blobs in annotations.

[datakurre]

/cc @hvelarde @cguardia @ericof

[datakurre]

The actual issue here seem to be that deepcopying a blob results a new blob with zero data (bug or a feature of ZODB blob support?). And CMFEditions does its default versioning with deepcopy.

To reproduce:

1. create a new Plone site with Mosaic
2. add a new page with image tile and save the page
3. blobdirectory should contain 2 blobs, one for the image and another for its scale
4. edit page and save without changes
5. blobdirectory should contain 4 blobs, two of them being zero sized

(Or such copy.deepcopy and commit some blob anywhere.)

Not sure, what our CMFEditions' modifier(s) should do or where it should be located.

[datakurre]

For those, who want to dig into Plone versioning history, Nathan had minimal example for checking (and deleting) annotations of some object history:

http://stackoverflow.com/questions/10413409/cleaning-up-annotations-in-plones-cmfeditions-history-objects

[datakurre]

@esteele This is the versioning related blocker, which we discussed earlier.