exec-file, exec-env: support extracting sub-part

Add support for extracting sub-part of the document when running
exec-file or exec-env command.

Author: mikonieminen

cmd/sops/main.go

@@ -132,6 +132,10 @@ func main() {
 					Name:  "user",
 					Usage: "the user to run the command as",
 				},
+				cli.StringFlag{
+					Name:  "extract",
+					Usage: "extract a specific key or branch from the input document. Example: --extract '[\"somekey\"][0]'",
+				},
 			}, keyserviceFlags...),
 			Action: func(c *cli.Context) error {
 				if len(c.Args()) != 2 {
@@ -144,13 +148,20 @@ func main() {
 				inputStore := inputStore(c, fileName)
 
 				svcs := keyservices(c)
+
+				extract, err := parseTreePath(c.String("extract"))
+				if err != nil {
+					return common.NewExitError(fmt.Errorf("error parsing --extract path: %s", err), codes.InvalidTreePathFormat)
+				}
+
 				opts := decryptOpts{
 					OutputStore: &dotenv.Store{},
 					InputStore:  inputStore,
 					InputPath:   fileName,
 					Cipher:      aes.NewCipher(),
 					KeyServices: svcs,
 					IgnoreMAC:   c.Bool("ignore-mac"),
+					Extract:     extract,
 				}
 
 				output, err := decrypt(opts)
@@ -199,6 +210,10 @@ func main() {
 					Name:  "filename",
 					Usage: "filename for the temporarily file (default: tmp-file)",
 				},
+				cli.StringFlag{
+					Name:  "extract",
+					Usage: "extract a specific key or branch from the input document. Example: --extract '[\"somekey\"][0]'",
+				},
 			}, keyserviceFlags...),
 			Action: func(c *cli.Context) error {
 				if len(c.Args()) != 2 {
@@ -211,6 +226,11 @@ func main() {
 				inputStore := inputStore(c, fileName)
 				outputStore := outputStore(c, fileName)
 
+				extract, err := parseTreePath(c.String("extract"))
+				if err != nil {
+					return common.NewExitError(fmt.Errorf("error parsing --extract path: %s", err), codes.InvalidTreePathFormat)
+				}
+
 				svcs := keyservices(c)
 				opts := decryptOpts{
 					OutputStore: outputStore,
@@ -219,6 +239,7 @@ func main() {
 					Cipher:      aes.NewCipher(),
 					KeyServices: svcs,
 					IgnoreMAC:   c.Bool("ignore-mac"),
+					Extract:     extract,
 				}
 
 				output, err := decrypt(opts)
@@ -592,7 +613,7 @@ func main() {
 		},
 		cli.StringFlag{
 			Name:  "extract",
-			Usage: "extract a specific key or branch from the input document. Decrypt mode only. Example: --extract '[\"somekey\"][0]'",
+			Usage: "extract a specific key or branch from the input document. Example: --extract '[\"somekey\"][0]'",
 		},
 		cli.StringFlag{
 			Name:  "input-type",