Draft: Ignore tree-reference content
This is an equivalent of a git-submodule... How to deal with it properly is to be defined. In the mean time, let's ignore it if it's sensible enough.
TODO:
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Add a test case (it will be easier when the real fix is implemented if we have the case in there) -
Improve commit message
Refs. #4583
Edited by Antoine R. Dumont