Implement sops publish command (#473)

* Implement `sops publish` command

Publishes a file to a pre-configured destination (this lives in the sops
config file). Additionally, support re-encryption rules that work
just like the creation rules. Initial support for S3/GCS.

This is a part of the sops-workspace v2.0 project

Includes the addition of a new dependency:
  github.com/googleapis/gax-go/v2

* code review changes; support global --verbose flag

* Switch to recreation_rule with full support

Reencryption rule is now recreation rule and supports everything that a
creation rule does. Now, when you load a config for a file, you load
either the creation rule or the destination rule. I'm not sure about
this style long term, but it allows for support to be added for the
recreation rules without a bigger refactor of how the config file works.

* split loadForFileFromBytes into two functions

remove branching based on destination rule or not, create one for
creation rules and one for destination rules

* pretty diff for keygroup updates in sops publish

publish/gcs.go

@@ -0,0 +1,36 @@
+package publish
+
+import (
+	"context"
+	"fmt"
+
+	"cloud.google.com/go/storage"
+)
+
+type GCSDestination struct {
+	gcsBucket string
+	gcsPrefix string
+}
+
+func NewGCSDestination(gcsBucket string, gcsPrefix string) *GCSDestination {
+	return &GCSDestination{gcsBucket, gcsPrefix}
+}
+
+func (gcsd *GCSDestination) Path(fileName string) string {
+	return fmt.Sprintf("gcs://%s/%s%s", gcsd.gcsBucket, gcsd.gcsPrefix, fileName)
+}
+
+func (gcsd *GCSDestination) Upload(fileContents []byte, fileName string) error {
+	ctx := context.Background()
+	client, err := storage.NewClient(ctx)
+	if err != nil {
+		return err
+	}
+	wc := client.Bucket(gcsd.gcsBucket).Object(gcsd.gcsPrefix + fileName).NewWriter(ctx)
+	defer wc.Close()
+	_, err = wc.Write(fileContents)
+	if err != nil {
+		return err
+	}
+	return nil
+}

publish/publish.go

@@ -0,0 +1,6 @@
+package publish
+
+type Destination interface {
+	Upload(fileContents []byte, fileName string) error
+	Path(fileName string) string
+}

publish/s3.go

@@ -0,0 +1,38 @@
+package publish
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/s3"
+)
+
+type S3Destination struct {
+	s3Bucket string
+	s3Prefix string
+}
+
+func NewS3Destination(s3Bucket string, s3Prefix string) *S3Destination {
+	return &S3Destination{s3Bucket, s3Prefix}
+}
+
+func (s3d *S3Destination) Path(fileName string) string {
+	return fmt.Sprintf("s3://%s/%s%s", s3d.s3Bucket, s3d.s3Prefix, fileName)
+}
+
+func (s3d *S3Destination) Upload(fileContents []byte, fileName string) error {
+	sess := session.Must(session.NewSession())
+	svc := s3.New(sess)
+	input := &s3.PutObjectInput{
+		Body:   aws.ReadSeekCloser(bytes.NewReader(fileContents)),
+		Bucket: aws.String(s3d.s3Bucket),
+		Key:    aws.String(s3d.s3Prefix + fileName),
+	}
+	_, err := svc.PutObject(input)
+	if err != nil {
+		return err
+	}
+	return nil
+}