yanglint UPDATE extension validation (#2413)

Examples included.

Author: Ardival

tests/yanglint/interactive/data_operational.test

@@ -1,7 +1,7 @@
 source [expr {[info exists ::env(TESTS_DIR)] ? "$env(TESTS_DIR)/interactive/ly.tcl" : "ly.tcl"}]
 
 set ddir "$::env(TESTS_DIR)/data"
-set err1 "Operational datastore takes effect only with RPCs/Actions/Replies/Notification input data types"
+set err1 "Operational datastore takes effect only with RPCs/Actions/Replies/Notification/Extensions input data types"
 
 test data_operational_twice {it is not allowed to specify more than one --operational parameter} {
 -setup $ly_setup -cleanup $ly_cleanup -body {

tests/yanglint/non-interactive/data_operational.test

@@ -2,7 +2,7 @@ source [expr {[info exists ::env(TESTS_DIR)] ? "$env(TESTS_DIR)/non-interactive/
 
 set mdir "$::env(YANG_MODULES_DIR)"
 set ddir "$::env(TESTS_DIR)/data"
-set err1 "Operational datastore takes effect only with RPCs/Actions/Replies/Notification input data types"
+set err1 "Operational datastore takes effect only with RPCs/Actions/Replies/Notification/Extensions input data types"
 
 test data_operational_twice {it is not allowed to specify more than one --operational parameter} {
  ly_cmd_err "-t notif -O $ddir/modconfig.xml -O $ddir/modleaf.xml" "cannot be set multiple times"

tools/lint/cmd.c

@@ -70,7 +70,7 @@ COMMAND commands[] = {
  },
  {
  "data", cmd_data_opt, cmd_data_dep, cmd_data_store, cmd_data_process, cmd_data_help, NULL,
- "Load, validate and optionally print instance data", "d:ef:F:hmo:O:R:r:nt:x:"
+ "Load, validate and optionally print instance data", "d:ef:F:hmo:O:R:r:nt:x:k:"
  },
  {
  "list", cmd_list_opt, cmd_list_dep, cmd_list_exec, NULL, cmd_list_help, NULL,

tools/lint/cmd.h

@@ -381,6 +381,15 @@ int cmd_debug_dep(struct yl_opt *yo, int posc);
  */
 int cmd_debug_store(struct ly_ctx **ctx, struct yl_opt *yo, const char *posv);
 
+/**
+ * @brief Store the values: mod_name, name, argument of extension.
+ *
+ * @param[in] extension_id String in format "<module-name>:<extension-name>:<argument>".
+ * @param[in,out] yo Options for yanglint.
+ * @return 0 on success.
+ */
+int parse_ext_string(const char *extension_id, struct yl_opt *yo);
+
 /**
  * @brief Set debug logging.
  *