Support JSON output in vitastor-disk prepare and purge

src/disk_tool/disk_tool.cpp

@@ -68,6 +68,7 @@ static const char *help_text =
     "    --data_device_block 4k     Override data device block size\n"
     "    --meta_device_block 4k     Override metadata device block size\n"
     "    --journal_device_block 4k  Override journal device block size\n"
+    "    --json                     Enable JSON output\n"
     "  \n"
     "  immediate_commit setting is automatically derived from \"disable fsync\" options.\n"
     "  It's set to \"all\" when fsync is disabled on all devices, and to \"small\" if fsync\n"
@@ -102,6 +103,7 @@ static const char *help_text =
     "    --move-meta TARGET       move metadata to TARGET\n"
     "    --journal-size NEW_SIZE  resize journal to NEW_SIZE\n"
     "    --data-size NEW_SIZE     resize data device to NEW_SIZE\n"
+    "    --json                   enable JSON output\n"
     "    --dry-run                only show new layout, do not apply it\n"
     "  \n"
     "  NEW_SIZE may include k/m/g/t suffixes.\n"
@@ -131,10 +133,11 @@ static const char *help_text =
     "  Commands are passed to systemctl with vitastor-osd@<num> units as arguments.\n"
     "  When --now is added to enable/disable, OSDs are also immediately started/stopped.\n"
     "\n"
-    "vitastor-disk purge [--force] [--allow-data-loss] <device> [device2 device3 ...]\n"
+    "vitastor-disk purge [--json] [--force] [--allow-data-loss] <device> [device2 device3 ...]\n"
     "  Purge Vitastor OSD(s) on specified device(s). Uses vitastor-cli rm-osd to check\n"
     "  if deletion is possible without data loss and to actually remove metadata from etcd.\n"
     "  --force and --allow-data-loss options may be used to ignore safety check results.\n"
+    "  --json enables JSON output.\n"
     "  \n"
     "  Requires `vitastor-cli`, `sfdisk` and `partprobe` (from parted) utilities.\n"
     "\n"