Non-convergent balanced trees share same digest

[MatthieuNICOLAS]

Severity: Low

Problem

Two balanced trees with the same totally ordered set of blocks, but distinct because balanced differently, share the same digest.

Consequence

Since we rely mostly on the digest to compare documents models in our tests, this can hide the fact that the models are unexpectedly not strongly convergent.

Possible fix

• digest() could be updated to take into account the shape of the tree.
• We could provide another function treeDigest() to keep track separately of the convergence of the content and of the model.