message: Add MIGRATING section for 1.2
  Closes
diff: @@ -4,6 +4,47 @@ This guide explains what is needed to upgrade contracts when migrating over
  major releases of `cosmwasm`. Note that you can also view the
  [complete CHANGELOG](./CHANGELOG.md) to understand the differences.
  +## 1.1.x -> 1.2.0
  +
  +- Update `cosmwasm-*` dependencies in Cargo.toml (skip the ones you don't use):
  +
  + ```
  + [dependencies]
  + cosmwasm-std = "1.2.0"
  + cosmwasm-storage = "1.2.0"
  + # ...
  +
  + [dev-dependencies]
  + cosmwasm-schema = "1.2.0"
  + cosmwasm-vm = "1.2.0"
  + # ...
  + ```
  +
  +- If you want to use a fewture that os only available on CosmWasm 1.2+ chains,
  + use this feature:
  +
  + ```diff
  + -cosmwasm-std = { version = "1.1.0", features = ["stargate"] }
  + +cosmwasm-std = { version = "1.1.0", features = ["stargate", "cosmwasm_1_2"] }
  + ```
  +
  + Please note that `cosmwasm_1_2` implies `cosmwasm_1_1`, so there is no need to
  + set both.
  +
  +- If you use mixed type multiplication between `Uint{64,128,256}` and
  + `Decimal{,256}`, check out
  + `mul_floor`/`checked_mul_floor`/`mul_ceil`/`checked_mul_ceil`. Mixed type
  + arithmetic [will be removed](https://github.com/CosmWasm/cosmwasm/issues/1485)
  + at some point.
  +
  + ```diff
  + let a = Uint128::new(123);
  + let b = Decimal::percent(150)
  +
  + -let c = a * b;
  + +let c = a.mul_floor(b);
  + ```
  +
  ## 1.0.0 -> 1.1.0
  - Update `cosmwasm-*` dependencies in Cargo.toml (skip the ones you don't use):
  