git-annex has some interesting tagging functionality. It uses trees of symlinks to provide the virtual filesystem: http://git-annex.branchable.com/metadata/ htt

git-annex has some interesting tagging functionality. It uses trees of symlinks to provide the virtual filesystem: http://git-annex.branchable.com/metadata/ http://git-annex.branchable.com/metadata/ and http://git-annex.branchable.com/tips/metadata_driven_views/ http://git-annex.branchable.com/tips/metadata_driven_views/