add cache-from

cmd/drone-docker/main.go

@@ -150,6 +150,10 @@ func main() {
 			Name:   "target",
 			Usage:  "build target",
 			EnvVar: "PLUGIN_TARGET",
+		cli.StringSliceFlag{
+			Name:   "cache-from",
+			Usage:  "cache from",
+			EnvVar: "PLUGIN_CACHE_FROM",
 		},
 		cli.BoolFlag{
 			Name:   "squash",
@@ -245,6 +249,7 @@ func run(c *cli.Context) error {
 			Target:      c.String("target"),
 			Squash:      c.Bool("squash"),
 			Pull:        c.BoolT("pull-image"),
+			CacheFrom:   c.String("cache-from"),
 			Compress:    c.Bool("compress"),
 			Repo:        c.String("repo"),
 			Labels:      c.StringSlice("custom-labels"),

docker.go

@@ -47,6 +47,7 @@ type (
 		Target      string   // Docker build target
 		Squash      bool     // Docker build squash
 		Pull        bool     // Docker build pull
+		CacheFrom   string   // Docker build cache-from
 		Compress    bool     // Docker build compress
 		Repo        string   // Docker build repository
 		LabelSchema []string // label-schema Label map
@@ -104,6 +105,15 @@ func (p Plugin) Exec() error {
 		fmt.Println("Registry credentials not provided. Guest mode enabled.")
 	}
 
+	// pre-pull cache image
+	if p.Build.CacheFrom != "" {
+		cmd := commandPull(p.Build.CacheFrom)
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		trace(cmd)
+		cmd.Run()
+	}
+
 	if p.Build.Squash && !p.Daemon.Experimental {
 		fmt.Println("Squash build flag is only available when Docker deamon is started with experimental flag. Ignoring...")
 		p.Build.Squash = false
@@ -162,6 +172,10 @@ func commandLogin(login Login) *exec.Cmd {
 	)
 }
 
+func commandPull(repo string) *exec.Cmd {
+	return exec.Command(dockerExe, "pull", repo)
+}
+
 func commandLoginEmail(login Login) *exec.Cmd {
 	return exec.Command(
 		dockerExe, "login",
@@ -204,6 +218,9 @@ func commandBuild(build Build) *exec.Cmd {
 	if build.NoCache {
 		args = append(args, "--no-cache")
 	}
+	if build.CacheFrom != "" {
+		args = append(args, "--cache-from", build.CacheFrom)
+	}
 	for _, arg := range build.ArgsEnv {
 		addProxyValue(&build, arg)
 	}