fenics

utils::ptr_vector<T> serves a similar purpose like smart pointers from std. We should remove this implementation in favor of smart pointers from std.

I already took care of replacing utils::ptr_vector<T> with std::unique_ptr in precice/precice#1159, but there are many more places, where utils::ptr_vector<T> is used.

The actual ghostUpdate is truly needed only in very few places, for most local operations one knows the value for ghosts without communication.

This

u.vector.copy(result=u0.vector)
u0.vector.ghostUpdate(addv=PETSc.InsertMode.INSERT, mode=PETSc.ScatterMode.FORWARD)

could become

with u0.vector.localForm() as loc0, u.vector.localForm() as loc:
    loc.copy(loc0)
``

While converting the developer docs docuemnt to markdown I stumbled
upon the envvar directive. I think it would be nice to use that generally,
but it needs some work. For one all variables from environment.rst show
up as second level TOC entries in the main navigation now. Which is something
we do not want. The developer docs should also use the referencing mechanism
and maybe we want to add a