Automatic equation numbering when referencing with :ref:

[benRenard]

In the Sphynx doc, the equation number in references to equations is hard-coded, e.g. :
The likelihood function in :ref:`equation 3 <math_num_documentation.bayesian_estimation.likelihood>`

It would be nice to be able to use automatic numbering, e.g. something that could look like:
The likelihood function in :ref:`equation %s <math_num_documentation.bayesian_estimation.likelihood>`

Apparently it's doable by playing with the numref/numfig/etc. options in conf.py.