The tokens in this repo implement EIP621, which includes facility for increasing and decreasing a token's total supply. There are two implemented tokens in the repo, EIP621Token and EIP621OraclizedToken.
In EIP621Token, the increase and decrease supply functions are public methods. This adheres to the spec strictly speaking, but may not be super useful.
In EIP621OraclizedToken, a supply oracle is set in the contract's constructor which may increase and decrease the supply.