refactor: Drop offset in favor of ignoring the first index

cmd/stbak/cmd/archive.go

@@ -173,7 +173,6 @@ var archiveCmd = &cobra.Command{
 			int(lastIndexedBlock),
 			viper.GetBool(overwriteFlag),
 
-			0,
 			func(hdr *tar.Header, i int) error {
 				if len(hdrs) <= i {
 					return errMissingTarHeader

cmd/stbak/cmd/recovery_index.go

@@ -77,7 +77,6 @@ var recoveryIndexCmd = &cobra.Command{
 			viper.GetInt(blockFlag),
 			viper.GetBool(overwriteFlag),
 
-			0,
 			func(hdr *tar.Header, i int) error {
 				return encryption.DecryptHeader(hdr, viper.GetString(encryptionFlag), identity)
 			},

cmd/stbak/cmd/update.go

@@ -119,13 +119,16 @@ var updateCmd = &cobra.Command{
 			int(lastIndexedBlock),
 			false,
 
-			1,
 			func(hdr *tar.Header, i int) error {
-				if len(hdrs) <= i {
+				if i == 0 {
+					return nil
+				}
+
+				if len(hdrs) <= i-1 {
 					return errMissingTarHeader
 				}
 
-				*hdr = *hdrs[i]
+				*hdr = *hdrs[i-1]
 
 				return nil
 			},

pkg/recovery/index.go

@@ -32,7 +32,6 @@ func Index(
 	block int,
 	overwrite bool,
 
-	offset int,
 	decryptHeader func(
 		hdr *tar.Header,
 		i int,
@@ -129,18 +128,16 @@ func Index(
 				break
 			}
 
-			if i >= offset {
-				if err := decryptHeader(hdr, i-offset); err != nil {
-					return err
-				}
+			if err := decryptHeader(hdr, i); err != nil {
+				return err
+			}
 
-				if err := verifyHeader(hdr, isRegular); err != nil {
-					return err
-				}
+			if err := verifyHeader(hdr, isRegular); err != nil {
+				return err
+			}
 
-				if err := indexHeader(record, block, hdr, metadataPersister, pipes.Compression, pipes.Encryption); err != nil {
-					return nil
-				}
+			if err := indexHeader(record, block, hdr, metadataPersister, pipes.Compression, pipes.Encryption); err != nil {
+				return nil
 			}
 
 			curr, err := f.Seek(0, io.SeekCurrent)
@@ -215,18 +212,16 @@ func Index(
 				}
 			}
 
-			if i >= offset {
-				if err := decryptHeader(hdr, i-offset); err != nil {
-					return err
-				}
+			if err := decryptHeader(hdr, i); err != nil {
+				return err
+			}
 
-				if err := verifyHeader(hdr, isRegular); err != nil {
-					return err
-				}
+			if err := verifyHeader(hdr, isRegular); err != nil {
+				return err
+			}
 
-				if err := indexHeader(record, block, hdr, metadataPersister, pipes.Compression, pipes.Encryption); err != nil {
-					return nil
-				}
+			if err := indexHeader(record, block, hdr, metadataPersister, pipes.Compression, pipes.Encryption); err != nil {
+				return nil
 			}
 
 			curr = int64(counter.BytesRead)