This is OPAL >= 1.9.9. Be aware of the fact that the documentation is not anymore a seperate project.
The documentation is in this repository in the directory 'doc' (https://gitlab.psi.ch/OPAL/src/tree/master/doc).
On machines with LaTeX the User's Reference Manual can be built in the same directory as the code by configuring cmake using -DENABLE_DOCUMENTATION=1 to enable the compilation.
The manual can then be built by calling 'make doc'. If you want to compile the manual every time you compile the code then set -DEXCLUDE_DOC_FROM_ALL=0 .