tar: add -k and -o to --help

    -o	Don't restore user:group
    -k	Don't replace existing files

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/tar.c b/archival/tar.c
index 415ebde..4515d42 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -776,6 +776,9 @@
 //usage:     "\n	-f FILE	Name of TARFILE ('-' for stdin/out)"
 //usage:     "\n	-C DIR	Change to DIR before operation"
 //usage:     "\n	-v	Verbose"
+//usage:     "\n	-o	Don't restore user:group"
+///////:-p - accepted but ignored, restores mode (aliases in GNU tar: --preserve-permissions, --same-permissions)
+//usage:     "\n	-k	Don't replace existing files"
 //usage:	IF_FEATURE_SEAMLESS_Z(
 //usage:     "\n	-Z	(De)compress using compress"
 //usage:	)
@@ -811,9 +814,6 @@
 //usage:       "$ tar -cf /tmp/tarball.tar /usr/local\n"
 
 // Supported but aren't in --help:
-//	o	no-same-owner
-//	p	same-permissions
-//	k	keep-old
 //	no-recursion
 //	numeric-owner
 //	no-same-permissions