Deduplicate digests from user configuration (#2522)

* deduplicate digests from user configuration

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* backout pointer reciever change on imageSource

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

---------

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

internal/file/digest.go

@@ -22,6 +22,7 @@ func supportedHashAlgorithms() []crypto.Hash {
 }
 
 func NewDigestsFromFile(closer io.ReadCloser, hashes []crypto.Hash) ([]file.Digest, error) {
+	hashes = NormalizeHashes(hashes)
 	// create a set of hasher objects tied together with a single writer to feed content into
 	hashers := make([]hash.Hash, len(hashes))
 	writers := make([]io.Writer, len(hashes))
@@ -67,7 +68,7 @@ func Hashers(names ...string) ([]crypto.Hash, error) {
 		}
 		hashers = append(hashers, hashObj)
 	}
-	return hashers, nil
+	return NormalizeHashes(hashers), nil
 }
 
 func CleanDigestAlgorithmName(name string) string {

internal/file/normalize_hashes.go

@@ -0,0 +1,24 @@
+package file
+
+import (
+	"crypto"
+	"sort"
+
+	"github.com/scylladb/go-set/uset"
+)
+
+func NormalizeHashes(hashes []crypto.Hash) []crypto.Hash {
+	set := uset.New()
+	for _, h := range hashes {
+		set.Add(uint(h))
+	}
+	list := set.List()
+	sort.Slice(list, func(i, j int) bool {
+		return list[i] < list[j]
+	})
+	result := make([]crypto.Hash, len(list))
+	for i, v := range list {
+		result[i] = crypto.Hash(v)
+	}
+	return result
+}

internal/file/normalize_hashes_test.go

@@ -0,0 +1,44 @@
+package file
+
+import (
+	"crypto"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNormalizeHashes(t *testing.T) {
+
+	tests := []struct {
+		name  string
+		input []crypto.Hash
+		want  []crypto.Hash
+	}{
+		{
+			name: "deduplicate hashes",
+			input: []crypto.Hash{
+				crypto.SHA1,
+				crypto.SHA1,
+			},
+			want: []crypto.Hash{
+				crypto.SHA1,
+			},
+		},
+		{
+			name: "sort hashes",
+			input: []crypto.Hash{
+				crypto.SHA512,
+				crypto.SHA1,
+			},
+			want: []crypto.Hash{
+				crypto.SHA1,
+				crypto.SHA512,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, NormalizeHashes(tt.input))
+		})
+	}
+}