btrfs-progs: use NULL instead of 0

These were mostly in option structs but there were a few gross string
pointer arguments given as 0.

Signed-off-by: Zach Brown <zab@redhat.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/commands.h b/commands.h
index 3f12fab..0600a58 100644
--- a/commands.h
+++ b/commands.h
@@ -50,6 +50,8 @@ struct cmd_struct {
 	int hidden;
 };
 
+#define NULL_CMD_STRUCT {NULL, NULL, NULL, NULL, 0}
+
 struct cmd_group {
 	const char * const *usagestr;
 	const char *infostr;