ktutil: Add import command and other improvements

- Add an import command that imports JSON as output by
   `ktutil list --json --keys`.

   This is enables one to filter/edit keytabs with jq!

 - Add a `merge` alias for the `copy` command, since that's effectively
   what it does.

 - Add a `--copy-duplicates` option to the `copy`/`merge` command.

 - Add a `--no-create` option to the `get` command.

 - Add a `--no-change-keys` option to the `get` command.

 - Make `add` complain if it can't finish writing to the keytab.

admin/ktutil-commands.in

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2004 Kungliga Tekniska Högskolan
+ * Copyright (c) 2004-2022 Kungliga Tekniska Högskolan
  * (Royal Institute of Technology, Stockholm, Sweden). 
  * All rights reserved. 
  *
@@ -151,11 +151,17 @@ command = {
 }
 command = {
 	name = "copy"
+	name = "merge"
 	function = "kt_copy"
+	option = {
+		long = "copy-duplicates"
+		type = "flag"
+		help = "copy entries for the same principal and kvno, but different keys"
+	}
 	argument = "source destination"
 	min_args = "2"
 	max_args = "2"
-	help = "Copies one keytab to another."
+	help = "Merges one keytab into another."
 }
 command = {
 	name = "get"
@@ -166,6 +172,16 @@ command = {
 		help = "admin principal"
 		argument = "principal"
 	}
+	option = {
+		long = "create"
+		type = "-flag"
+		help = "do not create the principal"
+	}
+	option = {
+		long = "change-keys"
+		type = "-flag"
+		help = "do not change the principal's keys"
+	}
 	option = {
 		long = "enctypes"
 		short = "e"
@@ -214,6 +230,14 @@ command = {
 	argument = "principal..."
 	help = "Change keys for specified principals, and add them to the keytab."
 }
+command = {
+	name = "import"
+	function = "kt_import"
+	help = "Imports a keytab from JSON output of ktutil list --json --keys."
+        min_args = "0"
+        max_args = "1"
+	argument = "JSON-FILE"
+}
 command = {
 	name = "list"
 	option = {