add cache_to option and remove manual image pull (#46)

Port from https://github.com/thegeeklab/drone-docker-buildx/pull/124

Basically docker cache got a bit fancier and now includes a cache manifest. Manually pulling these containers isn't sufficient enough, so remove the manual pull.

cache_to allows you to push your cache including a manifest to a remote location: https://docs.docker.com/engine/reference/commandline/buildx_build/#cache-to

Unfortunately this option isn't quite that useful: to fully use this feature, you need to supply your arguments in CSV format, which woodpecker unhelpfully splits into multiple completely separate arguments, breaking it :(

With a further change to fix that issue I managed to turn a multistage rust build from ~3 minutes down to 20 seconds.

Co-authored-by: miniduikboot <mini@duikbo.at>
Reviewed-on: https://codeberg.org/woodpecker-plugins/plugin-docker-buildx/pulls/46
Reviewed-by: 6543 <6543@obermui.de>
Co-authored-by: miniduikboot <miniduikboot@noreply.codeberg.org>
Co-committed-by: miniduikboot <miniduikboot@noreply.codeberg.org>

cmd/docker-buildx/config.go

@@ -183,6 +183,12 @@ func settingsFlags(settings *plugin.Settings) []cli.Flag {
 			Usage:       "sets images to consider as cache sources",
 			Destination: &settings.Build.CacheFrom,
 		},
+		&cli.StringSliceFlag{
+			Name:        "cache-to",
+			EnvVars:     []string{"PLUGIN_CACHE_TO"},
+			Usage:       "cache destination for the build cache",
+			Destination: &settings.Build.CacheTo,
+		},
 		&cli.BoolFlag{
 			Name:        "pull-image",
 			EnvVars:     []string{"PLUGIN_PULL_IMAGE"},

plugin/docker.go

@@ -10,15 +10,6 @@ import (
 	"github.com/urfave/cli/v2"
 )
 
-// helper to check if args match "docker pull <image>"
-func isCommandPull(args []string) bool {
-	return len(args) > 2 && args[1] == "pull"
-}
-
-func commandPull(repo string) *exec.Cmd {
-	return exec.Command(dockerExe, "pull", repo)
-}
-
 func commandLoginEmail(login Login) *exec.Cmd {
 	return exec.Command(
 		dockerExe, "login",
@@ -86,6 +77,9 @@ func commandBuild(build Build, dryrun bool) *exec.Cmd {
 	for _, arg := range build.CacheFrom.Value() {
 		args = append(args, "--cache-from", arg)
 	}
+	for _, arg := range build.CacheTo.Value() {
+		args = append(args, "--cache-to", arg)
+	}
 	for _, arg := range build.ArgsEnv.Value() {
 		addProxyValue(&build, arg)
 	}

plugin/impl.go

@@ -61,6 +61,7 @@ type Build struct {
 	Output          string          // Docker build output
 	Pull            bool            // Docker build pull
 	CacheFrom       cli.StringSlice // Docker build cache-from
+	CacheTo         cli.StringSlice // Docker build cache-to
 	Compress        bool            // Docker build compress
 	Repo            cli.StringSlice // Docker build repository
 	NoCache         bool            // Docker build no-cache
@@ -271,12 +272,6 @@ func (p *Plugin) Execute() error {
 	cmds = append(cmds, commandInfo())    // docker info
 	cmds = append(cmds, commandBuilder(p.settings.Daemon))
 	cmds = append(cmds, commandBuildx())
-
-	// pre-pull cache images
-	for _, img := range p.settings.Build.CacheFrom.Value() {
-		cmds = append(cmds, commandPull(img))
-	}
-
 	cmds = append(cmds, commandBuild(p.settings.Build, p.settings.Dryrun)) // docker build
 
 	// execute all commands in batch mode.
@@ -286,9 +281,7 @@ func (p *Plugin) Execute() error {
 		trace(cmd)
 
 		err := cmd.Run()
-		if err != nil && isCommandPull(cmd.Args) {
+		if err != nil {
-			fmt.Printf("Could not pull cache-from image %s. Ignoring...\n", cmd.Args[2])
-		} else if err != nil {
 			return err
 		}
 	}