Fix usage message to mention -c_opacity

diff --git a/cmd/gvmap/gvmap.c b/cmd/gvmap/gvmap.c
index 1c2528112479cf61853c2dbf1523a48feaed9da0..85784800bda3776dbeb1ab885170f31053726877 100644 (file)
--- a/cmd/gvmap/gvmap.c
+++ b/cmd/gvmap/gvmap.c
@@ -190,6 +190,7 @@ static char* usestr =
        6 : sequential single hue red \n\
        7 : sequential single hue lighter red \n\
        8 : light grey\n\
+    -c_opacity=xx - 2-character hex string for opacity of polygons\n\
     -C k - generate at most k clusters. (0)\n\
     -d s - seed used to calculate Fielder vector for optimal coloring\n\
     -e   - show edges\n\