[PATCH 3/4] parseopt: make usage optional

["René Scharfe" <rene.scharfe@lsrfire.ath.cx>]

Allow usagestr to be NULL and don't display anything a help screen in
this case.  This is useful to implement incremental parsers.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
---
 parse-options.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/parse-options.c b/parse-options.c
index 8b21dea..51e804b 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -364,6 +364,9 @@ int parse_options(int argc, const char **argv, const struct option *options,
 int usage_with_options_internal(const char * const *usagestr,
 				const struct option *opts, int full)
 {
+	if (!usagestr)
+		return PARSE_OPT_HELP;
+
 	fprintf(stderr, "usage: %s\n", *usagestr++);
 	while (*usagestr && **usagestr)
 		fprintf(stderr, "   or: %s\n", *usagestr++);
-- 
1.6.2