chore(cli): add S3 bucket object tree to svc show (#4966)

sample output:
```
% copilot svc show 
Service name: static-site
About

  Application  bugbash-static
  Name         static-site
  Type         Static Site

Routes

  Environment  URL
  -----------  ---
  test         d1vwytbnh1k1gy.cloudfront.net
  prod         d1yb44q5409rdj.cloudfront.net

S3 Bucket Objects

  Environment  test
.
├── error.html
├── index.html
├── css
│   ├── Style.css
│   ├── all.min.css
│   └── bootstrap.min.css
└── images
    ├── bg-masthead.jpg
    └── new
        └── hi.html

  Environment  prod
.
├── ReadMe.md
├── error.html
├── index.html
├── Images
│   ├── AWS-free.PNG
│   ├── S3WebsiteHosting-Architecture.PNG
│   ├── SampleWebsite.PNG
│   ├── Step1-CreateBucket-B.PNG
│   ├── Step1-CreateBucket-C.PNG
│   ├── Step1-CreateBucket-D.PNG
│   ├── Step1-CreateBucket-E.PNG
│   ├── Step1-CreateBucket.PNG
│   ├── Step2-UploadContents.PNG
│   ├── Step3-BucketPolicy-A.PNG
│   ├── Step3-BucketPolicy-B.PNG
│   ├── Step3-BucketPolicy.PNG
│   ├── Step4-A.PNG
│   └── Step4-B.PNG
├── css
│   ├── Style.css
│   ├── all.min.css
│   └── bootstrap.min.css
└── images
    ├── bg-masthead.jpg
    └── new
        └── hi.html
```

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the Apache 2.0 License.

internal/pkg/aws/ecr/ecr_test.go

@@ -413,15 +413,15 @@ func TestClearRepository(t *testing.T) {
 			},
 			wantError: nil,
 		},
-		"returns error if fail to check repo existance": {
+		"returns error if fail to check repo existence": {
 			mockECRClient: func(m *mocks.Mockapi) {
 				m.EXPECT().DescribeImages(&ecr.DescribeImagesInput{
 					RepositoryName: aws.String(mockRepoName),
 				}).Return(nil, mockAwsError)
 			},
 			wantError: fmt.Errorf("ecr repo mockRepoName describe images: %w", mockAwsError),
 		},
-		"returns error if fail to check repo existance because of non-awserr error type": {
+		"returns error if fail to check repo existence because of non-awserr error type": {
 			mockECRClient: func(m *mocks.Mockapi) {
 				m.EXPECT().DescribeImages(&ecr.DescribeImagesInput{
 					RepositoryName: aws.String(mockRepoName),

internal/pkg/aws/s3/s3.go

@@ -7,6 +7,7 @@ package s3
 import (
 	"errors"
 	"fmt"
+	"github.com/xlab/treeprint"
 	"io"
 	"mime"
 	"path/filepath"
@@ -30,6 +31,9 @@ const (
 
 	// Object location prefixes.
 	s3URIPrefix = "s3://"
+
+	// Delimiter for ListObjectsV2Input.
+	slashDelimiter = "/"
 )
 
 type s3ManagerAPI interface {
@@ -38,6 +42,7 @@ type s3ManagerAPI interface {
 
 type s3API interface {
 	ListObjectVersions(input *s3.ListObjectVersionsInput) (*s3.ListObjectVersionsOutput, error)
+	ListObjectsV2(input *s3.ListObjectsV2Input) (*s3.ListObjectsV2Output, error)
 	DeleteObjects(input *s3.DeleteObjectsInput) (*s3.DeleteObjectsOutput, error)
 	HeadBucket(input *s3.HeadBucketInput) (*s3.HeadBucketOutput, error)
 }
@@ -77,13 +82,12 @@ func (s *S3) EmptyBucket(bucket string) error {
 	var listResp *s3.ListObjectVersionsOutput
 	var err error
 
-	// Bucket is exists check to make sure the bucket exists before proceeding in emptying it
-	isExists, err := s.isBucketExists(bucket)
+	bucketExists, err := s.bucketExists(bucket)
 	if err != nil {
-		return fmt.Errorf("unable to determine the existance of bucket %s: %w", bucket, err)
+		return fmt.Errorf("unable to determine the existence of bucket %s: %w", bucket, err)
 	}
 
-	if !isExists {
+	if !bucketExists {
 		return nil
 	}
 
@@ -190,8 +194,7 @@ func FormatARN(partition, location string) string {
 	return fmt.Sprintf("arn:%s:s3:::%s", partition, location)
 }
 
-// Check whether the bucket exists before proceeding with empty the bucket
-func (s *S3) isBucketExists(bucket string) (bool, error) {
+func (s *S3) bucketExists(bucket string) (bool, error) {
 	input := &s3.HeadBucketInput{
 		Bucket: aws.String(bucket),
 	}
@@ -206,6 +209,87 @@ func (s *S3) isBucketExists(bucket string) (bool, error) {
 	return true, nil
 }
 
+// GetBucketTree retrieves the objects in an S3 bucket and creates an ASCII tree representing their folder structure.
+func (s *S3) GetBucketTree(bucket string) (string, error) {
+	exists, err := s.bucketExists(bucket)
+	if err != nil {
+		return "", err
+	}
+	if !exists {
+		return "", nil
+	}
+
+	var contents []*s3.Object
+	var prefixes []*s3.CommonPrefix
+	listResp := &s3.ListObjectsV2Output{}
+	for {
+		listParams := &s3.ListObjectsV2Input{
+			Bucket:            aws.String(bucket),
+			Delimiter:         aws.String(slashDelimiter),
+			ContinuationToken: listResp.NextContinuationToken,
+		}
+		listResp, err = s.s3Client.ListObjectsV2(listParams)
+		if err != nil {
+			return "", fmt.Errorf("list objects for bucket %s: %w", bucket, err)
+		}
+		contents = append(contents, listResp.Contents...)
+		prefixes = append(prefixes, listResp.CommonPrefixes...)
+		if listResp.NextContinuationToken == nil {
+			break
+		}
+	}
+
+	tree := treeprint.New()
+	// Add top-level files.
+	for _, object := range contents {
+		tree.AddNode(aws.StringValue(object.Key))
+	}
+	// Recursively add folders and their children.
+	if err := s.addNodes(tree, prefixes, bucket); err != nil {
+		return "", err
+	}
+	return tree.String(), nil
+}
+
+func (s *S3) addNodes(tree treeprint.Tree, prefixes []*s3.CommonPrefix, bucket string) error {
+	if len(prefixes) == 0 {
+		return nil
+	}
+
+	listResp := &s3.ListObjectsV2Output{}
+	var err error
+	for _, prefix := range prefixes {
+		var respContents []*s3.Object
+		var respPrefixes []*s3.CommonPrefix
+		branch := tree.AddBranch(filepath.Base(aws.StringValue(prefix.Prefix)))
+		for {
+			listParams := &s3.ListObjectsV2Input{
+				Bucket:            aws.String(bucket),
+				Delimiter:         aws.String(slashDelimiter),
+				ContinuationToken: listResp.ContinuationToken,
+				Prefix:            prefix.Prefix,
+			}
+			listResp, err = s.s3Client.ListObjectsV2(listParams)
+			if err != nil {
+				return fmt.Errorf("list objects for bucket %s: %w", bucket, err)
+			}
+			respContents = append(respContents, listResp.Contents...)
+			respPrefixes = append(respPrefixes, listResp.CommonPrefixes...)
+			if listResp.NextContinuationToken == nil {
+				break
+			}
+		}
+		for _, file := range respContents {
+			fileName := filepath.Base(aws.StringValue(file.Key))
+			branch.AddNode(fileName)
+		}
+		if err := s.addNodes(branch, respPrefixes, bucket); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (s *S3) upload(bucket, key string, buf io.Reader) (string, error) {
 	in := &s3manager.UploadInput{
 		Body:        buf,