It appeared that by merging bitcoin_hashes and patching we could do changes into multiple crates. Unfortunately, this doesn't include secp256k which forms a "hole" in our crate tree, so everything breaks when we need to do a breaking change to bitcoin_hashes.

This cannot be easily fixed by using git dependencies and/or having a separate branch because we need to merge rust-bitcoin before secp256k1 can compile but we can't compile rust-bitcoin before secp256k1 is merged. Perhaps the only solution, apart from merging these repositories too, is to have a temporary branch that doesn't require tests to pass.

Any other ideas?

Note: setting P-high because this blocks development, specifically #1481