Minecraft wiki entry for Development_versions, associated text: Can have filter section in pack.mcmeta now.
This section has mandatory field block, which is a list of patterns (regular expressions) for namespaces and paths.
If any of files in packs added before one with filter section matches any pattern inside block, it will be filtered out (i.e. treated as if it wasn't present in the first place).
filter section does not apply to a pack containing it, only to packs loaded before it.
Both namespace and path can be omitted: if they are, the game works as if they had been specified as a ".*". Missing field matches every value. When they are included, these fields contain a regular expression pattern.
For example, adding pack with this section in pack.mcmeta after vanilla pack will hide all recipes and advancements defined by vanilla pack: