prettify --help output and add it to Readme.org

Readme.org

@@ -20,7 +20,21 @@ https://wiki.call-cc.org/man/5/Extension%20tools#changing-the-repository-locatio
 ~make~
 
 * Usage
-You'll also need a C compiler, so pick any.
+** Summary
+#+begin_src
+Usage: sexc [options] filename [-- options-for-c-compiler]
+Options:
+ --c-compiler=ARG         Select C compiler. Defaults to value of SEX_CC
+                          environment variable, or if it is empty, to cc
+ -c, --compile-object     Compile object file instead of executable program
+ -E, --preprocess         Emit C code
+ --public-interface       Get module's public interface
+ -h, --help               Show this help
+ -m, --macro-expand       Emit macro-expanded Sex code
+ -o, --output=ARG         Write output to file. Default file name is a.out.
+                          If -E or -m options are provided, defaults to stdout
+#+end_src
+** Compiling Hello World
 #+begin_src
 sexc ./examples/hell-world.sex -o hello
 #+end_src

sexc.scm

@@ -278,7 +278,9 @@
 ;;; Main function facilities
 
 (define opts-grammar
-  `((c-compiler "Select C compiler. Defaults to value of SEX_CC environment variable, or if it is empty, to cc"
+  (let ((padding 26))
+    `((c-compiler ,(fmt #f "Select C compiler. Defaults to value of SEX_CC" nl
+                        (pad padding) "environment variable, or if it is empty, to cc")
                   (required #f)
                   (value #t))
       (compile-object "Compile object file instead of executable program"
@@ -300,10 +302,11 @@
                     (required #f)
                     (value #f)
                     (single-char #\m))
-    (output "Write output to file. Default file name is a.out. If -E or -m options are provided, defaults to stdout"
+      (output ,(fmt #f "Write output to file. Default file name is a.out." nl
+                    (pad padding) "If -E or -m options are provided, defaults to stdout")
               (required #f)
               (value #t)
-            (single-char #\o))))
+              (single-char #\o)))))
 
 (define (print-help)
   (fmt #t "Usage: sexc [options] filename [-- options-for-c-compiler]\n")