When run with an expression, configures the content that is required to be held in the repository.
For example:
git annex required . "include=*.mp3 or include=*.ogg"
Without an expression, displays the current required content setting of the repository.
While git-annex-wanted(1) is just a preference, this designates content that should really not be
removed. For example a file that is wanted can be removed with gitannexdrop, but if that file is
required, it would need to be removed with gitannexdrop--force.
Also, git-annexfsck will warn about required contents that are not present.