started using clap to parse arguments

Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Elisabeth Henry <liz.henry@ouvaton.org>"]
 description = "Yet another converter from Markdown file to (HTML, LaTeX, Epub)"
 repository = "https://github.com/lise-henry/crowbook"
 readme = "README.md"
-keywords = "markdown, book"
+keywords = ["markdown", "book"]
 license = "mit"
 
 [lib]
@@ -22,3 +22,4 @@ pulldown-cmark = "0.0.7"
 mustache = "0.6"
 chrono = "0.2"
 uuid = "0.1"
+clap = "2"

src/bin/main.rs

@@ -1,25 +1,34 @@
 extern crate crowbook;
+extern crate clap;
 
 use crowbook::{Book};
 use std::env;
+use clap::{App,Arg};
 
 fn main() {
-    let mut args = env::args();
-    args.next(); //discard program name
+    let mut app = App::new("crowbook")
+        .version(env!("CARGO_PKG_VERSION"))
+        .author("Élisabeth Henry")
+        .about("Render a markdown book in Epub, PDF or HTML")
+        .arg_from_usage("-v, --verbose 'Activate verbose mode'")
+        .arg_from_usage("-o, --output=[FILE] 'Specifies an output file'")
+        .arg(Arg::with_name("book")
+             .index(1)
+             .required(true)
+             .help("A file containing the book configuration"));
 
-    match args.next() {
-        None => println!("Needs the name of a book config file"),
-        Some(ref s) => {
-            match Book::new_from_file(s) {
-                Ok(book) => {
-                    if let Err(err) = book.render_all()  {
-                        println!("{}", err);
-                    }
-                }
-                Err(err) => {
+    let matches = app.get_matches();
+
+    if let Some(s) = matches.value_of("book") {
+        match Book::new_from_file(s) {
+            Ok(book) => {
+                if let Err(err) = book.render_all()  {
                     println!("{}", err);
                 }
             }
+            Err(err) => {
+                println!("{}", err);
+            }
         }
     }
 }