Improve hist closed options desc

README.md

@@ -201,7 +201,7 @@ Usage: uplot histogram [options] <in.tsv>
 
 Options for histogram:
         --symbol VAL         character to be used to plot the bars
-        --closed VAL
+        --closed VAL         side of the intervals to be closed [left]
     -n, --nbins VAL          approximate number of bins
 
 Options:

lib/youplot/command/parser.rb

@@ -183,7 +183,7 @@ module YouPlot
             parser.on_head('-n', '--nbins VAL', Numeric, 'approximate number of bins') do |v|
               params.nbins = v
             end
-            parser.on_head('--closed VAL', String) do |v|
+            parser.on_head('--closed VAL', String, 'side of the intervals to be closed [left]') do |v|
               params.closed = v
             end
             parser.on_head('--symbol VAL', String, 'character to be used to plot the bars') do |v|