Add artifact commands

Implement build, push, pull and tag artifact commands.
For authentication purposes, all `flux <verb> artifact` commands are using the '~/.docker/config.json' config file and the Docker credential helpers.

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

cmd/flux/push_artifact.go

@@ -0,0 +1,99 @@
+/*
+Copyright 2022 The Flux authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+
+	"github.com/fluxcd/flux2/internal/oci"
+)
+
+var pushArtifactCmd = &cobra.Command{
+	Use:   "artifact",
+	Short: "Push artifact",
+	Long: `The push artifact command creates a tarball from the given directory and uploads the artifact to a OCI repository.
+The push command uses the credentials from '~/.docker/config.json'.`,
+	Example: `# Push the local manifests to GHCR
+flux push artifact  ghcr.io/org/manifests/app:v0.0.1 \
+	--path="./path/to/local/manifests" \
+	--source="$(git config --get remote.origin.url)" \
+	--revision="$(git branch --show-current)/$(git rev-parse HEAD)"
+`,
+	RunE: pushArtifactCmdRun,
+}
+
+type pushArtifactFlags struct {
+	path     string
+	source   string
+	revision string
+}
+
+var pushArtifactArgs pushArtifactFlags
+
+func init() {
+	pushArtifactCmd.Flags().StringVar(&pushArtifactArgs.path, "path", "", "Path to the directory where the Kubernetes manifests are located.")
+	pushArtifactCmd.Flags().StringVar(&pushArtifactArgs.source, "source", "", "The source address, e.g. Git URL.")
+	pushArtifactCmd.Flags().StringVar(&pushArtifactArgs.revision, "revision", "", "The source revision in the format '<branch|tag>/<commit-sha>'")
+	pushCmd.AddCommand(pushArtifactCmd)
+}
+
+func pushArtifactCmdRun(cmd *cobra.Command, args []string) error {
+	if len(args) < 1 {
+		return fmt.Errorf("artifact name is required")
+	}
+	url := args[0]
+
+	if pushArtifactArgs.source == "" {
+		return fmt.Errorf("--source is required")
+	}
+
+	if pushArtifactArgs.revision == "" {
+		return fmt.Errorf("--revision is required")
+	}
+
+	if pushArtifactArgs.path == "" {
+		return fmt.Errorf("invalid path %q", pushArtifactArgs.path)
+	}
+
+	if fs, err := os.Stat(pushArtifactArgs.path); err != nil || !fs.IsDir() {
+		return fmt.Errorf("invalid path %q", pushArtifactArgs.path)
+	}
+
+	meta := oci.Metadata{
+		Source:   pushArtifactArgs.source,
+		Revision: pushArtifactArgs.revision,
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), rootArgs.timeout)
+	defer cancel()
+
+	logger.Actionf("pushing artifact to %s", url)
+
+	digest, err := oci.Push(ctx, url, pushArtifactArgs.path, meta)
+	if err != nil {
+		return fmt.Errorf("pushing artifact failed: %w", err)
+	}
+
+	logger.Successf("artifact successfully pushed to %s", digest)
+
+	return nil
+
+}