Document only-dirs option

contrib/man/exa.1

@@ -107,6 +107,11 @@ ignore files mentioned in '.gitignore'
 list directories before other files
 .RS
 .RE
+.TP
+.B \-D, \-\-only\-dirs
+list only directories
+.RS
+.RE
 .SH LONG VIEW OPTIONS
 .PP
 These options are available when running with \f[C]\-\-long\f[]

src/options/help.rs

@@ -27,6 +27,7 @@ FILTERING AND SORTING OPTIONS
   -r, --reverse              reverse the sort order
   -s, --sort SORT_FIELD      which field to sort by
   --group-directories-first  list directories before other files
+  -D, --only-dirs            list only directories
   -I, --ignore-glob GLOBS    glob patterns (pipe-separated) of files to ignore
   --git-ignore               Ignore files mentioned in '.gitignore'
   Valid sort fields:         name, Name, extension, Extension, size, type,