[PATCH v2] erofs-utils: introduce long parameter option

[Gao Xiang]

From: Li Guifu <blucerlee at gmail.com>

Only long option "--help" is valid now.

Signed-off-by: Li Guifu <blucerlee at gmail.com>
Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
---
changes since v1:
 - update based on
   https://lore.kernel.org/r/20191022025053.GA180717@architecture4/

 mkfs/main.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/mkfs/main.c b/mkfs/main.c
index 71c81f59e5b6..d3ebc8f55bda 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -13,6 +13,7 @@
 #include <limits.h>
 #include <libgen.h>
 #include <sys/stat.h>
+#include <getopt.h>
 #include "erofs/config.h"
 #include "erofs/print.h"
 #include "erofs/cache.h"
@@ -23,6 +24,11 @@
 
 #define EROFS_SUPER_END (EROFS_SUPER_OFFSET + sizeof(struct erofs_super_block))
 
+static struct option long_options[] = {
+	{"help", no_argument, 0, 1},
+	{0, 0, 0, 0},
+};
+
 static void usage(void)
 {
 	fprintf(stderr, "usage: [options] FILE DIRECTORY\n\n");
@@ -32,6 +38,7 @@ static void usage(void)
 	fprintf(stderr, " -x#       set xattr tolerance to # (< 0, disable xattrs; default 2)\n");
 	fprintf(stderr, " -EX[,...] X=extended options\n");
 	fprintf(stderr, " -T#       set a fixed UNIX timestamp # to all files\n");
+	fprintf(stderr, " --help    display this help and exit\n");
 }
 
 static int parse_extended_opts(const char *opts)
@@ -96,7 +103,8 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 	char *endptr;
 	int opt, i;
 
-	while ((opt = getopt(argc, argv, "d:x:z:E:T:")) != -1) {
+	while((opt = getopt_long(argc, argv, "d:x:z:E:T:",
+				 long_options, NULL)) != -1) {
 		switch (opt) {
 		case 'z':
 			if (!optarg) {
@@ -146,6 +154,10 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 			}
 			break;
 
+		case 1:
+			usage();
+			exit(0);
+
 		default: /* '?' */
 			return -EINVAL;
 		}
-- 
2.17.1