btrfs-progs: warn when an experimental functionality is used

Print warning when one of the following is requested by some command
line option:

- btrfstune -b: conversion to block-group-tree
- mkfs.btrfs --num-global-roots: extent-tree-v2
- btrfs-image -d: dump image with data

Issue: #523
Signed-off-by: David Sterba <dsterba@suse.com>

btrfstune.c

@@ -966,7 +966,7 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
 			break;
 		switch(c) {
 		case 'b':
-			btrfs_warn_experimental("Feature: block-group-tree");
+			btrfs_warn_experimental("Feature: conversion to block-group-tree");
 			to_bg_tree = true;
 			break;
 		case 'S':
@@ -1004,9 +1004,10 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
 			break;
 #if EXPERIMENTAL
 		case GETOPT_VAL_CSUM:
+			btrfs_warn_experimental(
+				"Switching checksums is experimental, do not use for valuable data!");
 			ctree_flags |= OPEN_CTREE_SKIP_CSUM_CHECK;
 			csum_type = parse_csum_type(optarg);
-			warning("Switching checksums is experimental, do not use for valuable data!");
 			printf("Switch csum to %s\n",
 					btrfs_super_csum_name(csum_type));
 			break;

image/main.c

@@ -3109,6 +3109,7 @@ int BOX_MAIN(image)(int argc, char *argv[])
 			multi_devices = 1;
 			break;
 		case 'd':
+			btrfs_warn_experimental("Feature: dump image with data");
 			dump_data = true;
 			break;
 		case GETOPT_VAL_HELP:

mkfs/main.c

@@ -1188,6 +1188,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 				csum_type = parse_csum_type(optarg);
 				break;
 			case GETOPT_VAL_GLOBAL_ROOTS:
+				btrfs_warn_experimental("Feature: num-global-roots is part of exten-tree-v2");
 				nr_global_roots = (int)arg_strtou64(optarg);
 				break;
 			case GETOPT_VAL_HELP: