lvmconfig: add --valuesonly option

The new --valuesonly option causes the lvmconfig output to contain only
values without keys for each config node. This is practical mainly in
case where we use lvmconfig in scripts and we want to assign the value
to a different custom key or simply output the value itself without the
key.

For example:

  # lvmconfig --type full activation/raid_fault_policy
  raid_fault_policy="warn"

  # lvmconfig --type full activation/raid_fault_policy --valuesonly
  "warn"

  # my_var=$(lvmconfig --type full activation/raid_fault_policy --valuesonly)

  # echo $my_var
  "warn"

1 files changed, 7 insertions, 0 deletions

diff --git a/tools/dumpconfig.c b/tools/dumpconfig.c
index 9e4408e16..4a0f193c4 100644
--- a/tools/dumpconfig.c
+++ b/tools/dumpconfig.c
@@ -242,6 +242,10 @@ int dumpconfig(struct cmd_context *cmd, int argc, char **argv)
 			log_error("--withgeneralpreamble has no effect with --type list");
 			return EINVALID_CMD_LINE;
 		}
+		if (arg_is_set(cmd, valuesonly_ARG)) {
+			log_err("--valuesonly has no effect with --type list");
+			return EINVALID_CMD_LINE;
+		}
 		/* list type does not require status check */
 	} else if (!strcmp(type, "full")) {
 		tree_spec.type = CFG_DEF_TREE_FULL;
@@ -320,6 +324,9 @@ int dumpconfig(struct cmd_context *cmd, int argc, char **argv)
 	if (arg_is_set(cmd, withspaces_ARG))
 		tree_spec.withspaces = 1;
 
+	if (arg_is_set(cmd, valuesonly_ARG))
+		tree_spec.valuesonly = 1;
+
 	if (cft_check_handle)
 		tree_spec.check_status = cft_check_handle->status;