feat: add support for building docker actions with private registries (#1557)

This commit adds a new `LoadDockerAuthConfigs` function, which loads all
registry auths that are configured on the host and sends them with the build
command to the docker daemon.

This is needed in case act builds a docker action and the images referenced in
that docker action are located on private registries or otherwise require
authentication (e.g. to get a higher rate limit).

The code is adapted from how the docker cli works:
257ff41304/cli/command/image/build.go (L323-L332)

Co-authored-by: Markus Wolf <mail@markus-wolf.de>

Co-authored-by: Markus Wolf <mail@markus-wolf.de>

pkg/container/docker_auth.go

@@ -38,3 +38,24 @@ func LoadDockerAuthConfig(ctx context.Context, image string) (types.AuthConfig,
 
 	return types.AuthConfig(authConfig), nil
 }
+
+func LoadDockerAuthConfigs(ctx context.Context) map[string]types.AuthConfig {
+	logger := common.Logger(ctx)
+	config, err := config.Load(config.Dir())
+	if err != nil {
+		logger.Warnf("Could not load docker config: %v", err)
+		return nil
+	}
+
+	if !config.ContainsAuth() {
+		config.CredentialsStore = credentials.DetectDefaultStore(config.CredentialsStore)
+	}
+
+	creds, _ := config.GetAllCredentials()
+	authConfigs := make(map[string]types.AuthConfig, len(creds))
+	for k, v := range creds {
+		authConfigs[k] = types.AuthConfig(v)
+	}
+
+	return authConfigs
+}

pkg/container/docker_build.go

@@ -44,6 +44,7 @@ func NewDockerBuildExecutor(input NewDockerBuildExecutorInput) common.Executor {
 			Tags:        tags,
 			Remove:      true,
 			Platform:    input.Platform,
+			AuthConfigs: LoadDockerAuthConfigs(ctx),
 		}
 		var buildContext io.ReadCloser
 		if input.Container != nil {