Change Details

``` With schnorrsig if you need to tweak the secret key (for BIP32) you must use the keypair API to get compatible secret/public keys which you do by calling secp256k1_keypair_xonly_tweak_add(), but after that there's no currently a way to extract the secret key back for storage. so I added a secp256k1_keypair_seckey function to extract the key ``` Backport of secp256k1#845

``` With schnorrsig if you need to tweak the secret key (for BIP32) you must use the keypair API to get compatible secret/public keys which you do by calling secp256k1_keypair_xonly_tweak_add(), but after that there's no currently a way to extract the secret key back for storage. so I added a secp256k1_keypair_seckey function to extract the key ``` Backport of [[https://github.com/bitcoin-core/secp256k1/pull/845 | secp256k1#845]]

``` With schnorrsig if you need to tweak the secret key (for BIP32) you must use the keypair API to get compatible secret/public keys which you do by calling secp256k1_keypair_xonly_tweak_add(), but after that there's no currently a way to extract the secret key back for storage. so I added a secp256k1_keypair_seckey function to extract the key ``` Backport of [[https://github.com/bitcoin-core/secp256k1/pull/845 | secp256k1#845]]