Add support for cache-to in build process

Author: dh-seanmurphy

cmd/drone-docker/main.go

@@ -183,6 +183,11 @@ func main() {
 			Usage:  "images to consider as cache sources",
 			EnvVar: "PLUGIN_CACHE_FROM",
 		},
+		cli.StringFlag{
+			Name:   "cache-to",
+			Usage:  "images to consider as cache stores",
+			EnvVar: "PLUGIN_CACHE_TO",
+		},
 		cli.BoolFlag{
 			Name:   "squash",
 			Usage:  "squash the layers at build time",
@@ -370,6 +375,7 @@ func run(c *cli.Context) error {
 			Squash:              c.Bool("squash"),
 			Pull:                c.BoolT("pull-image"),
 			CacheFrom:           c.StringSlice("cache-from"),
+			CacheTo:             c.String("cache-to"),
 			Compress:            c.Bool("compress"),
 			Repo:                c.String("repo"),
 			Labels:              c.StringSlice("custom-labels"),

docker.go

@@ -61,6 +61,7 @@ type (
 		Squash              bool     // Docker build squash
 		Pull                bool     // Docker build pull
 		CacheFrom           []string // Docker build cache-from
+		CacheTo             string   // Docker build cache-to
 		Compress            bool     // Docker build compress
 		Repo                string   // Docker build repository
 		LabelSchema         []string // label-schema Label map
@@ -414,6 +415,9 @@ func commandBuild(build Build) *exec.Cmd {
 	for _, arg := range build.CacheFrom {
 		args = append(args, "--cache-from", arg)
 	}
+	if build.CacheTo != "" {
+		args = append(args, "--cache-to", build.CacheTo)
+	}
 	for _, arg := range build.ArgsEnv {
 		addProxyValue(&build, arg)
 	}