a bit o' spruce, from http://play.spruce.cf

spruce.json

{"flavor":"1.14.0","prune":["meta","secrets"],"env":["HOME=/home/user"],"cherry_pick":[],"yaml":[{"filename":"file1.yml","contents":"--- # hammer\nsecrets:\n  uaa_jwt_signing_key: |\n    aaaaaa\n    aaaaaaaaaaaaaaaaaa\n  uaa_jwt_signing_old_key: |\n    jsdfasdjkfggjnsdg\n     dsgsdgsd\n  \n\n"},{"filename":"file2.yml","contents":"--- # final\nfoo:\n  bar:\n    jwt:\n      policy:\n        active_key_id: default\n        keys:\n          default:\n            signingKey: (( grab secrets.uaa_jwt_signing_key ))\n          old:\n            signingKey: (( grab secrets.uaa_jwt_signing_old_key || \"\" ))\n        refreshTokenValiditySeconds: 604800\n        global:\n          refreshTokenValiditySeconds: 604800      \n          \n"}],"skip_eval":false,"fallback_append":false,"go_patch":false,"debug":false,"trace":false}