Add --sparse / -O to the manual, to --help, and to option processing (#45).

src/main/help.c

@@ -351,6 +351,9 @@ void display_help(void)
 		{ "-K", "--direct-io", NULL,
 		 N_("use direct I/O to bypass cache"),
 		 { 0, 0, 0, 0} },
+		{ "-O", "--sparse", NULL,
+		 N_("try to seek instead of writing null bytes"),
+		 { 0, 0, 0, 0} },
 		{ "-X", "--discard", NULL,
 		 N_("discard input instead of writing to output"),
 		 { 0, 0, 0, 0} },

src/main/options.c

@@ -612,6 +612,8 @@ opts_t opts_parse(unsigned int argc, char **argv)
 		{ "stop-at-size", 0, NULL, (int) 'S' },
 		{ "sync", 0, NULL, (int) 'Y' },
 		{ "direct-io", 0, NULL, (int) 'K' },
+		{ "sparse", 0, NULL, (int) 'O' },
+		{ "sparse-output", 0, NULL, (int) 'O' },
 		{ "discard", 0, NULL, (int) 'X' },
 		{ "store-and-forward", 1, NULL, (int) 'U' },
 		{ "remote", 1, NULL, (int) 'R' },
@@ -627,7 +629,7 @@ opts_t opts_parse(unsigned int argc, char **argv)
 	/*@+nullassign@ */
 	int option_index = 0;
 #endif				/* HAVE_GETOPT_LONG */
-	char *short_options = "hVpteIrab8kTA:fvnqcWD:s:gl0i:w:H:N:u:F:x:L:B:CEZ:SYKXU:R:P:d:m:o:"
+	char *short_options = "hVpteIrab8kTA:fvnqcWD:s:gl0i:w:H:N:u:F:x:L:B:CEZ:SYKOXU:R:P:d:m:o:"
 #ifdef ENABLE_DEBUGGING
 	    "!:"
 #endif
@@ -972,6 +974,10 @@ opts_t opts_parse(unsigned int argc, char **argv)
 		case 'K':
 			opts->direct_io = true;
 			break;
+		case 'O':
+			opts->sparse_output = true;
+			opts->no_splice = true;
+			break;
 		case 'X':
 			opts->discard_input = true;
 			opts->no_splice = true;